cooperative catalysis 
 between thioureas and brnsted acids , 
 whereby the enhanced catalytic activity of the thiourea acts as an 
 acid amplifier , has successfully been applied to asymmetric catalysis , and more recently , reports have emerged from 
 the schmidt group applying this type of synergistic catalysis to glycosylation 
 reactions involving o - glycosyl trichloroacetimidate 
 donors to yield -selective glycosides .
deoxy - hexoses are an important class of glycosides that occur 
 widely 
 in many natural products ranging from antibiotics to anticancer agents . the stereoselective formation of glycosidic linkages 
 employing 2-deoxyglycosides , where a substituent at c-2 that can direct 
 the coupling reaction is lacking , is a very challenging endeavor and 
 many efforts have been devoted to achieve their stereoselective synthesis .
acid - catalyzed direct nucleophilic substitution 
 on a glycal is one of the most widely used and efficient methods for 
 their synthesis , however these reactions often give anomeric mixtures 
 and side products ( e.g. , ferrier rearrangement side - products ) . as part of our ongoing 
 interest in developing stereoselective glycosylation methods , we decided to focus our attention on the synthesis 
 of deoxyglycosides . recently , our team reported a mild organocatalytic 
 method for the preparation of 2-deoxygalactosides employing schreiner s 
 thiourea with excellent yields and -selectivity .
although the method worked well with galactals , reactions needed 
 to be refluxed over 24 h to reach completion , and in general , the 
 thiourea catalyst was unable to activate glucal or rhamnal substrates . 

we postulated that synergistic acid / thiourea activation could provide 
 a more efficient and practical glycosylation strategy for the preparation 
 of deoxyglycosides than current methods that use hydrogen - bonding 
 organocatalysts or acids as the sole promoters ( scheme 1 ) . to evaluate our hypothesis ,
thiourea 1 was 
 chosen 
 as the organocatalyst based on previous successful work from our group 
 and others .
moreover , binol - derived 
 phosphoric acids have been shown to be particularly effective in many 
 asymmetric transformations , including 
 some success in glycosylations involving trichloroacetimidate glycoside 
 donors .
more recently , chiral phosphoric 
 acids have also been shown to catalyze the spiroketalization of cyclic 
 enol ethers bearing a pendant alcohol nucleophile in a highly diastereoselective syn - selective concerted mechanism whereby the phosphoric 
 acid acts as a bifunctional catalyst activating both the alkene and 
 alcohol nucleophile .
initial experiments began with the screening of a series of commercial 
 binol - derived phosphoric acids for their ability to promote the stereoselective 
 glycosylation of perbenzylated galactal 2a with glucoside 
 acceptor 3(12 ) in the absence 
 and presence of 1 in ch2cl2 at 
 room temperature .
as summarized in table 1 , coupling reactions employing 10 mol % of 
 chiral phosphoric acids ( s)-4a and ( r)-4b ( pka = 2.63 
 in dmso ) proceeded cleanly to give product 5(7 ) in 55 and 70% yields , albeit 
 after 20 h ( entries 2 and 4 ) and with different degrees of : 
 stereocontrol 9:1 and > 30:1 , respectively .
when 10 mol % of 1 was added as the cocatalyst ( entries 3 and 5 ) , reactions 
 were complete within 3 h , and glycoside 5 was obtained 
 in improved yields of 82% and 89% , respectively , and with an : 
 ratio of 7:1 for the ( s)-acid and > 30:1 for the 
 ( r)-acid catalyst .
these results demonstrate the 
 strong influence 
 of thiourea 1 , as a cocatalyst , on reaction rate and 
 yield , while the stereochemistry of the acid catalyst has the biggest 
 effect on the : selectivity of the glycosylation reaction . 

this observation is not completely surprising , as bennett and co - workers 
 had already reported that the stereo - outcome of acid - catalyzed glycosylation 
 reactions involving trichloroacetimidate donors was dependent on the 
 chirality of the catalyst , the configuration of the leaving group 
 in the glycoside donor , and the nature of the nucleophile acceptor .
it is important to note that glycosylation reactions 
 with 10 mol % of thiourea 1 in ch2cl2 ( in the absence of acid ) yielded only starting material ( entry 1 ) 
 as previously observed by our team , likely 
 due to catalyst inactivation via self - association at high catalyst 
 loading , further demonstrating the importance 
 of the synergy between both cocatalysts .
5 mol % , as reactions at 10 mol 
 % lead to rapid hydrolysis of 2a . from h nmr ; n / a = not 
 applicable
the use of achiral p - toluenesulfonic acid ( ptsoh , 5 mol % ) 4e or bis(4-nirophenyl)hydrogen 
 phosphate 4f or less acidic phosphoric catalysts 4c and 4d ( pka = 
 3.86 ) in combination with 1 proved to be detrimental to reaction rate , yield , and stereocontrol , 
 with reactions needing 620 h for completion ( entries 69 ) . 

next , we decided to explore the reaction conditions using 4b and 1 as the cocatalyst .
increasing the acid loading 
 to 20 mol % in the presence of 10 mol % of 1 had no effect 
 on the outcome of the model reaction ( entry 10 ) , while lowering the 
 reaction temperature significantly slowed product formation ( entry 
 11 ) . changing the reaction solvent to either mecn or diethyl ether 
 ( table 1 , entries 12 
 and 13 ) had a detrimental effect on the rate of the reaction . in the 
 case of mecn , which is known to participate during the glycosylation 
 reaction involving oxocarbenium ions favoring -glycoside products , significant erosion of the -selectivity 

was observed with 5 being isolated as a 3:1 : 
 mixture ( entry 11 vs entry 5 ) .
having established the optimum 
 reaction conditions , our attention 
 was then turned to exploring the scope of the cooperative catalytic 
 system on coupling reactions between 2a and a range of 
 oh nucleophiles 6a6j ( table 2 ) . in all cases , reactions proceeded 
 smoothly within 26 h and in excellent yields and -selectivity , 
 as determined by the characteristic anomeric signals in the h- and c nmr spectra , demonstrating that the catalytic system tolerates 
 the presence of common alcohol and amine protecting groups such as 
 acetals , ethers , esters , and carbamates .
glycosylations with primary 
 alcohols 6a6d and boc - protected 
 serine 6h afforded the corresponding glycoside products 
 in 8086% yield within 23 h and with a > 30:1 : 
 ratio ( entries 14 and 8) . reactions with secondary alcohols 
 such as phenols 6e , glycosides 6f and 6 g , boc - protected threonine 6i , or cholesterol 6j prove to be more challenging and required higher reaction 
 temperatures ( 45 c ) and the use of 20 mol % of 1 in combination with 10 mol % of 4b in ch2cl2 , to drive reactions to completion within 56 
 h. under these optimized conditions , the desired products were thus 
 isolated with similar high -selectivity ( > 30:1 : 
 ratio ) and yields of 7485% ( table 2 , entries 57 , 9 , and 10 ) .
reaction performed at 45 c , 
 1.5 equiv of donor and thiourea 1 ( 20 mol % ) ( 56 
 h ) .
product was isolated 
 as the desilylated 
 disaccharide for purification purposes . our attention then turned to exploring the scope of 
 the glycal 
 donor . to that end ,
a series of differentially protected galactals 2b2f , glucals 8a8c , and l - rhamnal 9 bearing methyl , 
 acetate , benzyl , allyl , silyl ether , and siloxane protecting groups 
 were prepared and subjected to the reaction conditions with 3 or 6k , which bears a secondary oh , as the acceptor 
 ( table 3 ) .
pleasingly , 
 high yields and excellent selectivities for -linked glycosides 
 were obtained in most examples ( entries 1 , 35 , and 7 ) .
although 
 substrate 2d , which bears an acetate group at c-6 , shows 
 that ester groups can be tolerated ( entry 3 ) , in the case of acetyl - protected 
 galactal 2c ( entry 2 ) , an inseparable mixture of glycosides 
 including ferrier side - products was observed 
 after 20 h under the more forcing conditions ( 20 mol % of 4b and reflux in ch2cl2 ) .
this lack of reactivity 
 has been previously noted for glycals bearing a deactivating group 
 ( e.g. , ester ) at c-3 , which is in close proximity to the reacting 
 double bond .
encouragingly , the reaction was 
 also amenable to glycosylations with glucal substrates , and both benzyl - derivative 8a and 3,4-o - siloxane protected 8b(6b ) or 8c(6b ) afforded the corresponding glycosides with high -stereocontrol 
 within 2 h , albeit 11a was isolated in a lower yield 
 ( 40% ) than 11b ( 81% yield ) or 11c ( 82% ) . 

this is not completely unexpected , as 8b has been shown 
 to be a more effective glycosylation donor than its benzylated counterpart 
 ( table 3 , entries 68 ) .
reaction 
 performed at 45 c , 
 1.5 equiv of donor , and 0.2 equiv of thiourea .
2,6-dideoxyglycosides are also an important class of compounds , 
 and their stereoselective synthesis is further complicated by the 
 lack of oxygen substituents at both c-2 and c-6 .
excitingly , activation of 3,4-o - siloxane 
 protected l - rhamnal 9 afforded 12 in 74% yield within 3 h and with an 8:1 : ratio ( entry 
 9 ) .
it is important to highlight that thiourea 1 alone 
 was not able to activate any of the glucal and rhamnal substrates . 

these results further emphasize that the synergistic catalytic system 
 works well across a range of reactivity profiles for both glycal donors 
 and nucleophile acceptors .
having found that thioglycosides 
 are inert under the cooperative 
 organocatalytic glycosylation conditions ( table 2 , entry 4 ) , we decided to evaluate the methodology 
 in a three - component , one - pot synthesis of trisaccharide 13 ( scheme 2 ) .
following disaccharide formation , 
 acceptor 6c was added to the same pot along with nis 
 and catalytic tmsotf and trisaccharide 13 was obtained 
 in 58% yield with complete stereoselectivity . to probe the mechanism 
 of our reaction ,
a 3:1 /-anomeric 
 mixture of 5 was subjected to the reaction conditions 
 and gave no change in the anomeric ratio , indicating that the high 
 -selectivity is not the result of anomerization . moreover , 

reaction with deuterated galactal 14 yielded disaccharide 15 with the newly formed bonds cis to each 
 other , as evidenced by the h nmr shifts associated with 
 h-1 (  4.62 ppm , d , 1h , j = 2.7 hz ) and h-2 
 (  2.031.99 , m , 1h , h-2 ) of the deuterated 2-deoxygalactoside ( scheme 3 ) , which suggest that both the c  h and the c  o 
 bond formation steps are syn - diastereoselective .
h nmr spectroscopy studies in cd2cl2 of mixtures of thiourea 1 and acid 4b showed 
 proton shifts associated with the aromatic signals from both acid 
 and thiourea , indicating that an interaction between both catalysts 
 occurs in solution . furthermore , nmr mixtures of thiourea 1 , acid 4b , and glycoside donor 2a showed 
 additional downfield h - shifts associated with the anomeric protons 
 in 2a (  6.33 ppm ) , while shifts for the oh signal 
 from acceptor 3 ( from  1.84 ppm to  2.54 
 ppm ) were detected in mixtures of 1 , 4b , 
 and 3 ( see supporting information for details ) .
thiourea 1 and chiral phosphoric acid 4b have been shown to individually hydrogen bond with oh nucleophiles .
as expected , mixtures of 3 and 10 mol % of thiourea 1 or 3 mixed with 10 mol % of acid 4b also showed shifts associated with the oh protons of glycosyl acceptor 3 , although the magnitude of those shifts was different to 
 that of mixtures of 3 and both cocatalysts ( 1 and 4b ) .
these results further demonstrate that the 
 combination of 1 and chiral acid ( r)-4b leads to a cooperative catalytic system that can activate 
 both enol ether and oh nucleophiles in a synergistic fashion , leading 
 to an enhancement in reaction rate and -stereocontrol of the 
 glycosylation reaction .
as proposed in scheme 3 , our findings suggest that a hydrogen - bond - mediated 
 complex between thiourea 1 and acid 4b leads 
 to a urea - induced acid amplification , and proton addition from this 
 complex to the less hindered face of the enol ether ( i ) forms a short - lived oxocarbenium intermediate ( ii ) 
 that is rapidly trapped by the oh nucleophile which is in turn activated 
 by the phosphate intermediate that is generated in situ , to give 15 .
this might help to explain the effect 
 the chirality of the phosphoric acid has on the stereo outcome of 
 the glycosylation reaction .
in summary , we have 
 described a practical , highly stereoselective , 
 and efficient direct glycosylation method for glycals using a cooperative 
 brnsted acid - organocatalytic promoter system .
the reaction is 
 widely applicable to a range of glycosyl donors and nucleophile acceptors , 
 proceeds with excellent yields and high selectivity for the -anomer , 
 and is tolerant of most common protecting groups .
we note that the 
 stereoselectivity of the reaction is highly dependent on the chirality 
 of the acid , with ( r)-4b leading to 
 the formation of -glycosides preferentially , while both yield 
 and rate of reaction are greatly enhanced by the synergistic interaction 
 between thiourea and acid .
moreover , we exemplify the generality of 
 the approach in the stereoselective synthesis of a series of disaccharides , 
 glycosyl - amino acids , and other glycoconjugates and also in the one - pot 
 chemo- and stereoselective synthesis of a trisaccharide
. further work 
 from our lab is underway to exploit the cooperative catalysis between 
 organocatalysts and chiral acids for the stereoselective synthesis 
 of other important glycosides and chiral acetals .
dry dcm was obtained by 
 distillation using 
 standard procedures or by passage through a column of anhydrous alumina . 

glassware and needles were either flame - dried immediately prior to 
 use or placed in an oven ( 150 c ) for at least 2 h and allowed 
 to cool either in a desiccators or under reduced pressure .
liquid 
 reagents , solutions , or solvents were added via syringe through rubber 
 septa .
detection was 
 by examination under uv light ( 254 nm ) and by charring with 10% sulfuric 
 acid in ethanol .
flash column chromatography was performed using silica 
 gel [ merck , 230400 mesh ( 4063 m ) ] .
extracts 
 were concentrated in vacuo using both a bchi 
 rotary evaporator ( bath temperatures up to 40 c ) at a pressure 
 of either 15 mmhg ( diaphragm pump ) or 0.1 mmhg ( oil pump ) , as appropriate , 
 and a high - vacuum line at room temperature .
h nmr and c nmr spectra were measured in the solvent stated at 400 
 or 500 mhz .
chemical shifts are quoted in parts per million from residual 
 solvent peak ( cdcl3 : h , 7.26 ppm and c , 77.16 ppm ) and coupling constants ( j ) given in 
 hertz .
multiplicities are abbreviated as bs ( broad ) , s ( singlet ) , 
 d ( doublet ) , t ( triplet ) , q ( quartet ) , m ( multiplet ) , or combinations 
 thereof .
positive ion matrix - assisted laser desorption ionization 
 time - of - flight ( maldi - tof ) mass spectra were recorded using an hp - maldi 
 instrument using gentisic acid matrix .
electrospray ionization ( esi ) 
 mass spectra were recorded on a micromass lct mass spectrometer or 
 a vg quattro mass spectrometer .
monosaccharide donor 
 ( 1 equiv ) and acceptor ( 0.83 equiv ( 0.1 mmol ) ) were weighed 
 into a microwave vial and placed under vacuum for 1 h , after which 
 time the microwave vial was filled with n2 .
a mixture of 
 chiral acid ( 0.1 equiv ) and thiourea ( 0.1 equiv for primary acceptors 
 and 0.2 equiv for secondary acceptors ) in anhydrous dcm ( 1 ml ) was 
 stirred for 30 min and then added to the microwave vial containing 
 the donor and acceptor .
the reaction mixture was stirred at rt ( primary 
 acceptors ) or heated at reflux ( secondary acceptors ) until the reaction 
 was determined to be complete by either tlc or nmr analysis of the 
 crude material .
the reaction mixture was purified by silica gel flash 
 column chromatography . following the general 
 glycosylation procedure , donor 2a ( 50 mg , 0.12 mmol ) 
 and acceptor 3 ( 46 mg , 0.10 mmol ) afforded the following 
 purification by column chromatography ( hexane : etoac , 6:1 to 3:1 ) : 5 as a yellow oil ( 68 mg , 89% ) .
h nmr ( 400 mhz ; 
 cdcl3 )  7.397.19 ( 30h , m , ph ) , 5.02 ( 1h , app d , j = 2.4 hz , h-1 ) , 4.98 ( 1h , d , j = 10.8 hz , och hph ) , 4.91 ( 1h , d , j = 11.6 hz , 
 och hph ) , 4.84 ( 1h , d , j = 10.9 hz , och hph ) , 4.80 
 ( 1h , d , j = 10.8 hz , ochh ph ) , 4.79 ( 1h , d , j = 12.2 hz , och hph ) , 4.68 ( 1h , d , j = 
 12.2 hz , ochh ph ) , 4.60 ( 1h , d , j = 3.6 hz , h-1 ) , 
 4.60 ( 1h , d , j = 11.6 hz , ochh ph ) , 4.57 ( 2h , s , 
 och2 ph ) , 4.52 ( 1h , d , j = 10.9 hz , ochh ph ) , 4.41 
 ( 1h , d , j = 12.0 hz , och hph ) , 4.34 ( 1h , d , j = 12.0 hz , ochh ph ) , 3.98 ( 1h , t , j = 
 9.2 hz , h-3 ) , 3.903.84 ( 3h , m , h-3 , h-4 , h-5 ) , 
 3.81 ( 1h , dd , j = 11.2 , 4.6 hz , h-6a ) , 3.72 ( 1h , 
 ddd , j = 10.0 , 4.5 , 1.6 hz , h-5 ) , 3.61 ( 1h , dd , j = 11.4 , 1.7 hz , h-6b ) , 3.54 ( 1h , dd , j = 9.5 , 7.3 hz , h-6a ) , 3.51 ( 1h , dd , j = 
 9.5 , 3.5 hz , h-2 ) , 3.50 ( 1h , dd , j = 9.5 , 5.9 hz , 
 h-6b ) , 3.46 ( 1h , dd , j = 9.9 , 9.0 hz , h-4 ) , 
 3.31(3h , s , och3 ) , 2.20 ( 1h , td , j = 12.4 , 3.7 hz , 
 h-2a ) , 2.01 ( 1h , app dd , j = 12.7 , 4.5 hz , 
 h-2b ) ; c nmr ( 126 mhz ; cdcl3 )  139.0 ( 4 
 c ) , 138.9 ( 4 c ) , 138.5 ( 4 c ) , 138.4 ( 4 c ) , 
 138.30 ( 4 c ) , 138.27 ( 4 c ) , 128.6 ( ch ) , 128.54 ( ch ) , 128.45 
 ( ch ) , 128.33 ( ch ) , 128.32 ( ch ) , 128.18 ( ch ) , 128.16 ( ch ) , 128.0 ( ch ) , 
 127.82 ( ch ) , 127.81 ( ch),127.78 ( ch ) , 127.7 ( ch ) , 127.6 ( ch ) , 127.5 
 ( ch ) , 98.4 ( c-1 ) , 98.0 ( c-1 ) , 82.3 ( c-3 ) , 80.1 ( c-2 ) , 78.1 
 ( c-4 ) , 76.0 ( c h2 ph ) , 75.1 ( c h2 ph ) , 74.41 , 74.35 ( c-3 , 
 c h2 ph ) , 73.5 ( c h2 ph ) , 73.4 ( c h2 ph ) , 73.1 ( c-4 ) , 70.4 , 
 70.2 ( c-5 , ch2ph ) , 70.0 ( c-5 ) , 69.5 ( c-6 ) , 66.2 ( c-6 ) , 
 55.2 ( och3 ) , 31.2 ( c-2 ) .
spectroscopic data in agreement with 
 literature . following the 
 general glycosylation procedure , donor 2a ( 50 mg , 0.12 
 mmol ) and acceptor 6a ( 11 mg , 0.10 mmol ) afforded the 
 following purification by column chromatography ( hexane : etoac , 10:1 
 to 8:1 ) : 7a as a colorless oil ( 42 mg , 80%).h nmr ( 500 mhz , cdcl3 )  7.377.22 ( 20h , 
 m , ph ) , 5.08 ( 1h , d , j = 3.5 hz , h-1 ) , 4.93 ( 1h , 
 d , j = 11.6 hz , ochhph ) , 4.67 ( 1h , 
 d , j = 11.9 hz , ochhph ) , 4.62 ( 1h , 
 d , j = 11.7 hz , ochhph ) , 4.59 ( 1h , 
 m , och2ph ) , 4.50 ( 1h , d , j = 11.8 hz , ochhph ) , 4.47 ( 2h , d , j = 11.9 hz , ochhph ) , 4.43 ( 1h , d , j = 11.8 hz , ochhph ) , 3.99 ( 1h , ddd , j = 12.0 , 4.6 , 2.5 hz , h-3 ) , 3.96 ( 1h , t , j = 6.7 
 hz , h-5 ) , 3.94 ( 1h , bs , h-4 ) , 3.61 ( 1h , dd , j = 9.4 , 
 6.8 hz , h-6a ) , 3.56 ( 1h , dd , j = 9.4 , 6.0 hz , h-6b ) , 
 2.25 ( 1h , td , j = 12.4 , 3.8 hz , h-2a ) , 2.072.01 
 ( 1h , m , h-2b ) ; c nmr ( 126 mhz , cdcl3 )  
 139.1 ( 4 c ) , 138.7 ( 4 c ) , 138.3 ( 4 c ) , 138.0 ( 4 
 c ) , 128.54 ( ch ) , 128.52 ( ch ) , 128.51 ( ch ) , 128.37 ( ch ) , 128.35 
 ( ch ) , 128.1 ( ch ) , 127.9 ( ch ) , 127.81 ( ch ) , 127.77 ( ch ) , 127.7 ( ch ) , 
 127.6 ( ch ) , 127.5 ( ch ) , 97.3 ( h-1 ) , 75.0 ( c-3 ) , 74.4 ( och2ph ) , 73.6 ( och2ph ) , 73.2 
 ( c-4 ) , 70.7 ( och2ph ) , 70.3 ( c-5 ) , 69.7 
 ( c-6 ) , 69.1 ( och2ph ) , 31.3 ( c-2 ) .
esi - hrms 
 for c34h36nao5 ( mna ) calcd : 547.2460 ; found : 547.2459 .
[ ]d = 
 + 24 ( c = 1 , chcl3 ) . following the general 
 glycosylation procedure , donor 2a ( 50 mg , 0.12 mmol ) 
 and acceptor 6b ( 50 mg , 0.10 mmol ) afforded the following 
 purification by column chromatography ( hexane : etoac , 6:1 to 4:1 ) : 7b as a white solid ( 79 mg , 86% )
donor 2a ( 50 mg , 0.12 
 mmol ) and acceptor 6x ( 26 mg , 0.10 mmol ) afforded the 
 following purification by column chromatography ( hexane : etoac , 6:1 
 to 3:1 ) 7c as a colorless oil ( 56 mg , 83% ) .
donor 2a ( 50 mg , 0.12 
 mmol ) and acceptor 6d ( 58 mg , 0.10 mmol ) afforded the 
 following purification by column chromatography ( hexane : etoac , 7:1 
 to 4:1 ) : 7d as a white solid ( 82 mg 82% ) .
spectroscopic 
 data in agreement with literature . following the 
 general glycosylation procedure , donor 2a ( 50 mg , 0.12 
 mmol ) and acceptor 6e ( 9 mg , 0.10 mmol ) afforded the 
 following purification by column chromatography ( hexane : etoac 20:1 
 to 12:1 ) : 7e as a colorless oil ( 43 mg 84% ) : h nmr ( 400 mhz ; cdcl3 )  7.426.98 ( 20h , 
 m , ph ) , 5.59 ( 1h , d , j = 3.4 hz , h-1 ) , 4.85 ( 1h , d , j = 11.5 hz , ochhph ) , 4.72 ( 2h , bs , och2ph ) , 4.67 ( 1h , d , j = 11.5 
 hz , ochhph ) , 4.28 ( 1h , d , j = 11.6 
 hz , ochhph ) , 4.24 ( 1h , d , j = 11.6 
 hz , ochhph ) , 4.02 ( 1h , ddd , h-3 ) , 3.93 ( 1h , t , j = 7.3 hz , h-5 ) , 3.80 ( 1h , bs , h-4 ) , 3.53 ( 1h , dd , j = 9.3 , 7.3 hz , h-6a ) , 3.40 ( 1h , dd , j = 9.3 , 5.7 hz , h-6b ) , 2.28 ( 1h , td , j = 12.4 , 3.6 
 hz , h-2a ) , 2.08 ( 1h , dd , j = 12.4 , 4.4 hz , h-2b ) ; c nmr ( 101 mhz ; cdcl3 )  156.8 ( 4 c ) , 
 138.8 ( 4 c ) , 138.4 ( 4 c ) , 138.0 ( 4 c ) , 128.4 ( ch ) , 
 128.3 ( ch ) , 128.2 ( ch ) , 128.2 ( ch ) , 128.1 ( ch ) , 128.2 ( ch ) , 127.7 
 ( ch ) , 127.6 ( ch ) , 127.5 ( ch ) , 127.3 ( ch ) , 121.9 ( ch ) , 116.6 ( ch ) , 
 96.5 ( c-1 ) , 74.5 ( ch2ph ) , 74.4 ( c-3 ) , 
 73.3 ( ch2ph ) , 72.8 ( c-4 ) , 70.6 ( ch2ph ) , 70.5 ( c-5 ) , 69.1 ( c-6 ) , 31.2 ( c-2 ) .
esi - hrms 
 for c33h34nao5 ( mna ) calcd : 533.2304 ; found : 533.2296 .
the general glycosylation 
 procedure was followed using donor 2a ( 50 mg , 0.12 mmol ) 
 and acceptor 6f ( 53 mg , 0.10 mmol ) .
the crude material 
 was then dissolved in a 1 m thf solution of tbaf ( 0.5 ml , 0.5 mmol ) 
 and stirred for 2 h. the solution was then concentrated in 
 vacuo and purified by column chromatography ( hexane : etoac , 
 6:1 to 4:1 ) , affording 7f as a colorless oil ( 58 mg , 
 74% ) .
donor 2a ( 50 mg , 0.12 mmol ) 
 and acceptor 6 g ( 26 mg , 0.10 mmol ) afforded the following 
 purification by column chromatography ( hexane : etoac , 6:1 to 3:1 ) : 7 g as a white solid ( 53 mg 78% ) .
spectroscopic data in agreement 
 with literature . following the general glycosylation 
 procedure , donor 2a ( 50 mg , 0.12 mmol ) and acceptor 6h ( 22 mg , 0.10 mmol ) 
 afforded the following purification by column chromatography ( hexane : etoac , 
 10:1 to 4:1 ) : 7h as a pale yellow oil ( 53 mg 83% ) .
donor 2a ( 50 mg , 0.12 mmol ) and acceptor 6i ( 23 mg , 
 0.10 mmol ) afforded the following purification by column chromatography 
 ( hexane : etoac , 10:1 to 4:1 ) : 7i as a pale yellow oil 
 ( 56 mg 85% ) .
h nmr ( 500 mhz ; cdcl3 )  
 7.377.23 ( 15h , m , ph ) , 5.14 ( 1h , j = 9.8 
 hz , nh ) , 4.944.89 ( 2h , m , h-1 , ochhph ) , 4.624.53 
 ( 3h , m , och2ph , h-6a ) , 4.51 ( 1h , d , j = 11.8 hz , ochhph ) , 4.43 ( 1h , d , j = 11.8 hz , ochhph ) , 4.304.25 
 ( 2h , m , ochhph , och(ch3)ch(nh ) ) , 3.943.89 ( 2h , m , h-6b , och(ch3)ch(nh ) ) , 3.84 ( 1h , m , h-3 ) , 3.72 ( 3h , s , och3 ) , 
 3.603.51 ( 2h , m , 2h-4 , h-5 ) , 2.15 ( 1h , td , j = 12.3 , 3.8 hz , h-2a ) , 1.86 ( 1h , dd , j = 12.4 , 
 4.4 hz , h-2b ) , 1.48 ( 9h , s , 3  ch3 ) , 1.25 ( 3h , d , j = 6.5 hz , och(ch3)ch(nh ) ) ; c nmr ( 126 mhz ; cdcl3 )  171.6 ( co ) , 156.0 
 ( co ) , 138.7 ( 4 c ) , 138.3 ( 4 c ) , 138.0 ( 4 c ) , 128.4 
 ( ch ) , 128.4 ( ch ) , 128.3 ( ch ) , 128.2 ( ch ) , 128.1 ( ch ) , 127.6 ( ch ) , 
 127.6 ( ch ) , 127.5 ( ch ) , 127.4 ( ch ) , 99.3 ( c-1 ) , 80.0 ( 4 c ) , 
 75.3 ( ch2ph ) , 74.2 ( ch2ph ) , 74.2 ( c-3 ) , 73.5 ( ch2ph ) , 72.9 ( c-4 ) , 70.3 [ och(ch3)ch(nh ) ] , 
 70.3 ( c-6 ) , 58.2 [ och(ch3)ch(nh ) ] , 52.2 
 ( och3 ) , 31.2 ( c-2 ) , 28.3 ( 3 x och3 ) , 18.3 [ och(ch3)ch(nh ) ] .
esi - hrms for c37h47no9na ( mna ) calcd : 672.3149 ; 
 found : 672.3144 .
[ ]d = + 20 ( c = 
 1 , chcl3 ) . following the 
 general glycosylation procedure , donor 2a ( 50 mg , 0.12 
 mmol ) and acceptor 6j ( 39 mg , 0.10 mmol ) afforded the 
 following purification by column chromatography ( hexane : etoac , 10:1 
 to 6:1 ) : 7j as a colorless oil ( 57 mg 74% ) .
spectroscopic 
 data in agreement with literature . following the 
 general glycosylation procedure , donor 2b ( 23 mg , 0.12 
 mmol ) and acceptor 3 ( 47 mg , 
 0.10 mmol ) afforded the following purification by column chromatography 
 ( hexane : etoac , 4:1 to 2:1 ) : 5b as a colorless oil ( 52 
 mg , 80% ) : h nmr ( 400 mhz ; cdcl3 )  7.417.22 
 ( 15h , m , ph ) , 5.024.96 ( 2h , m , h-1 , ochhph ) , 4.92 ( 1h , d , j = 10.9 hz , ochhph ) , 4.834.77 ( 2h , m , 2 ochhph ) , 4.68 ( 1h , 
 d , j = 12.2 hz , ochhph ) , 4.62 ( 1h , 
 d , j = 4.6 hz , ochhph ) , 4.60 ( 1h , 
 d , j = 2.9 hz , h-1 ) , 4.01 ( 1h , t , j = 9.2 hz , h-3 ) , 3.883.79 ( 2h , m , h-4 , 6a ) , 3.74 
 ( 1h , ddd , j = 9.9 , 4.4 , 1.8 hz , h-5 ) , 3.63 ( 1h , dd , j = 11.4 , 2.0 hz , h-6b ) , 3.613.56 ( 2h , m , 
 3,5 ) , 3.563.51 ( 5h , m , h-4 , och3 , h-2 ) , 3.513.40 ( 2h , m , h-6a , h-6b ) , 3.39 , 3.37 ( 6h , 
 2s , 2  och3 ) , 3.30 ( 3h , s , och3 ) , 2.041.90 
 ( 2h , m , h-2a,h-2b ) .
c nmr ( 101 mhz , cdcl3 )  138.6 ( 4 c ) , 138.2 ( 4 c ) , 138.1 ( 4 c ) , 
 128.5 ( ch ) , 128.4 ( ch ) , 128.4 ( ch ) , 128.1 ( ch ) , 128.1 ( ch ) , 127.9 
 ( ch ) , 127.7 ( ch ) , 98.2 ( c-1 ) , 97.9 ( c-1 ) , 82.1 ( c-3 ) , 80.0 
 ( c-2 ) , 77.8 ( c-1 ) , 75.9 , 75.8 , 74.9 ( c-3 , c-4 , c-5 ) , 
 74.4 ( ch2ph ) , 73.3 ( ch2ph ) , 71.5 ( ch2ph ) , 69.7 
 ( c-6 ) , 69.7 ( c-5 ) , 66.1 ( c-4 ) , 60.9 ( och3 ) , 59.1 ( och3 ) , 56.1 ( och3 ) , 55.1 ( och3 ) , 30.7 ( c-2 ) 
 .
esi - hrms for c37h48nao10 ( mna ) calcd : 675.3145 ; found : 675.3144 .
following the 
 general glycosylation procedure , donor 2d ( 50 mg , 0.12 
 mmol ) and acceptor 3 ( 47 mg , 0.10 mmol ) afforded the 
 following purification by column chromatography ( hexane : etoac 6:1 
 to 3:1 ) : 10d as a colorless oil ( 73 mg , 86% ) : h nmr ( 400 mhz ; cdcl3 )  7.417.19 ( 25h , 
 m , ph ) , 5.03 ( 1h , d , j = 3.3 hz , h-1 ) , 4.99 
 ( 1h , d , j = 10.7 hz , ochhph ) , 4.94 
 ( 1h , d , j = 11.7 hz , ochhph ) , 4.87 
 ( 1h , d , j = 11.0 hz , ochhph ) , 4.834.77 
 ( 2h , m , ochhph ) , 4.724.63 ( 2h , m , ochhph ) , 4.634.55 ( 3h , m , h-1 , ochhph ) , 4.48 ( 1h , d , j = 11.1 hz , ochhph ) , 4.113.95 ( 3h , m , h-3 , h-6a,h-6b ) , 3.84 
 ( 1h , ddd , j = 11.9 , 4.5 , 2.3 hz , h-3 ) , 3.74 
 ( 4h , m , h-4 , h-6a , h-2 , h-5 ) , 3.60 ( 1h , d , j = 10.5 hz , h-6b ) , 3.51 ( 1h , dd , j = 9.6 , 3.6 hz , 
 h-2 ) , 3.43 ( 1h , t , j = 9.3 hz , h-4 ) , 3.31 ( 3h , s , 
 och3 ) , 2.20 ( 1h , td , j = 12.3 , 3.6 hz , 
 h-2a ) , 2.03 ( 1h , dd , j = 12.5 , 4.4 hz , h-2b ) , 
 1.85 ( 3h , s , ch3co ) .
c nmr ( 101 mhz , cdcl3 )  170.5 ( ch3co ) 138.6 
 ( 4 c ) , 138.4 ( 4 c ) , 138.2 ( 4 c ) , 128.5 ( ch ) , 128.4 
 ( ch ) , 128.4 ( ch ) , 128.4 ( ch ) , 128.3 ( ch ) , 128.1 ( ch ) , 127.9 ( ch ) , 
 127.7 ( ch ) , 127.7 ( ch ) , 127.5 ( ch ) , 127.4 ( ch ) , 98.0 ( c-1 ) , 
 97.8 ( c-1 ) , 82.1 ( c-3 ) , 79.9 ( c-2 ) , 77.9 ( c-4 ) , 75.8 ( ch2ph ) , 74.9 ( ch2ph ) , 74.2 
 ( c-3 ) , 74.0 ( ch2ph ) , 73.2 ( ch2ph ) , 72.5 ( c-5 ) , 70.3 ( ch2ph ) , 69.7 ( h-4 ) , 69.1(h-5 ) , 65.9 ( c-6 ) , 64.0 
 ( c-6 ) , 55.0 ( och3 ) , 30.7 ( c-2 ) , 20.8 ( coch3 ) .
esi - hrms for c50h56nao11 ( mna ) calcd : 855.3720 ; found : 
 855.3711 .
[ ]d = + 8 ( c = 1 , chcl3 ) . following the 
 general glycosylation procedure , donor 2e ( 32 mg , 0.12 
 mmol ) and acceptor 3 ( 46 mg , 0.10 mmol ) afforded the 
 following purification by column chromatography ( hexane : etoac , 5:1 
 to 4:1 ) : 10e as a pale yellow oil ( 58 mg , 80% ) : h nmr ( 500 mhz ; cdcl3 )  7.417.22 
 ( 15h , m , ph ) , 6.005.79 ( 3h , m , ch = ch2 ) , 5.30 ( 1h , dt , j = 3.4 , 1.6 hz , ch = ch2 ) , 5.26 ( 1h , q , j = 1.8 hz , 
 ch = ch2 ) , 5.23 ( 1h , tt , j = 2.3 , 1.1 hz , ch = ch2 ) , 5.17 ( 1h , dt , j = 3.4 , 1.6 hz , ch = ch2 ) , 5.155.12 ( 2h , m , ch = ch2 ) , 5.01 ( 1h , d , j = 2.6 hz , 
 h-1 ) , 4.99 ( 1h , d , j = 10.8 hz , ochhph ) , 4.91 ( 1h , d , j = 10.8 hz , ochhph ) , 4.82 ( 1h , d , j = 5.3 hz , ochhph ) , 4.80 ( 1h , d , j = 6.6 hz , ochhph ) , 4.69 ( 1h , d , j = 12.2 hz , ochhph ) , 4.62 ( 1h , d , j = 2.5 hz , h-1 ) , 4.61 
 ( 1h , d , j = 4.8 hz , ochhph ) , 4.35 
 ( 1h , ddt , j = 12.7 , 5.6 , 1.4 hz , ochhch = ch2 ) , 4.134.06 ( 1h , m , ochhch = ch2 ) , 4.054.02 ( 2h , m , ochhch = ch2 , h-3 ) , 4.013.97 ( 1h , m , ochhch = ch2 ) , 3.943.91 ( 2h , ochhch = ch2 ) , 3.883.81 ( 2h , m , h-4 , 
 h-6a ) , 3.783.73 ( 3h , m , h-4 , h-3 , 
 h-5 ) , 3.64 ( 1h , dd , j = 11.4 , 2.0 hz , h-6b ) , 
 3.58 ( 1h , dd , j = 9.3 , 7.3 hz , h-5 ) , 3.563.52 
 ( 1h , m , h-2 ) , 3.513.46 ( 2h , m , h-6a , h-6b ) , 3.37 ( 3h , s , och3 ) , 2.142.07 ( 1h , m , h-2a ) , 1.951.90 
 ( 1h , m , h-2b).c nmr ( 126 mhz , cdcl3 )  138.7 ( 4 c ) , 138.2 ( 4 c ) , 138.1 ( 4 c ) , 
 135.6 ( ch = ch2 ) , 134.8 ( ch = ch2 ) , 134.6 ( ch = ch2 ) , 128.5 ( ch ) , 128.4 ( ch ) , 128.04 ( ch ) , 127.9 ( ch ) , 127.7 
 ( ch ) , 127.7 ( ch ) , 116.9 ( ch = ch2 ) , 116.8 ( ch = ch2 ) , 116.6 ( ch = ch2 ) , 98.2 ( c-1 ) , 97.9 ( c-1 ) , 82.1 ( c-3 ) , 
 80.0 ( c-5 ) , 77.9 ( c-2 ) , 75.8 ( ch2ph ) , 74.9 ( ch2ph ) , 73.9 ( c-4 ) , 
 73.5 ( och2ch ) , 73.3 ( ch2ph ) , 72.4 ( h-5 ) , 72.2 ( och2ch ) , 69.8 ( 2c , c-4 , c-3 ) , 69.2 ( och2ch ) , 69.1 ( c-6 ) , 66.0 ( c-6 ) , 55.0 ( och3 ) , 31.1 ( c-2 ) .
esi - hrms for c43h54nao10 ( mna ) calcd : 753.3615 ; found : 753.3610 . 

following the general glycosylation procedure , 
 donor 2f ( 50 mg , 0.10 mmol ) and acceptor 3 ( 39 mg , 0.09 mmol ) afforded the following purification by column 
 chromatography ( hexane : etoac , 5:1 to 4:1 ) : 10f as a colorless 
 oil ( 64 mg , 79% ) : h nmr ( 400 mhz , cdcl3 )  : 
 7.387.24 ( 15h , m , ph ) , 4.994.95 ( 2h , m , h-1 , 
 ochhph ) , 4.87 ( 1h , d , j = 10.8 hz , 
 ochhph ) , 4.83 ( 1h , d , j = 10.7 hz , 
 ochhph ) , 4.80 ( 1h , d , j = 12.2 hz , 
 ochhph ) , 4.67 ( 1h , d , j = 12.2 hz , 
 ochhph ) , 4.61 ( 1h , d , j = 10.8 hz , 
 ochhph ) , 4.57 ( 1h , d , j = 3.6 hz , 
 h-1 ) , 4.05 ( 1h , m , h-3 ) , 3.99 ( 1h , t , j = 
 9.2 hz , h-2 ) , 3.80 ( 1h , bs , h-4 ) , 3.773.73 ( 2h , m , 
 h-3 , h-6a ) ,
3.703.62 ( 4h , m , h-5 , h-6a , h-6b , 
 h-6b ) , 3.49 ( 1h , dd , j = 9.6 , 3.6 hz , h-4 ) , 
 3.42 ( 1h , t , j = 9.6 h-5 ) , 3.36 ( 3h , s , och3 ) , 2.08 ( 1h , td , j = 12.1 , 3.5 , h-2a ) , 1.65 
 ( 1h , dd , j = 12.7 , 4.5 h-2b ) , 0.940.86 
 ( 27h , m , 3  sic(ch3)3 ) , 0.120.00 
 ( 18h , m , 6 x sich3 ) ; c nmr ( 126 mhz ; cdcl3 ) 138.7 ( 4 c ) , 138.2 ( 4 c ) , 138.1 ( 4 c ) , 
 128.4127.7 ( ph ) , 97.9 ( c-1 ) , 97.6 ( c-1 ) , 82.1 ( c-2 ) , 
 79.9 ( c-4 ) , 78.5 ( c-5 ) , 75.8 ( och2ph ) , 
 75.1 ( och2ph ) , 73.3 ( och2ph ) , 72.7 ( c-5 ) , 70.3 ( c-4 ) , 68.3 ( c-3 ) , 
 65.2 ( c-6 ) , 62.6 ( c-6 ) , 54.7 ( och3 ) , 33.5 ( c-2 ) , 
 26.2 ( sic(ch3)3 ) , 26.1 ( sic(ch3)3 ) , 25.8 ( sic(ch3)3 ) , 18.6 ( sic(ch3)3 ) , 18.5 ( sic(ch3)3 ) , 18.1 ( sic(ch3)3 ) , 3.9 
 ( sich3 ) , 4.4 ( sich3 ) , 4.8 ( sich3 ) , 5.0 ( sich3 ) , 5.3 ( sich3 ) , 5.4 ( sich3 ) .
esi - hrms for c52h84nasi3o10 ( mna ) calcd : 975.5270 ; found : 975.5277 .
[ ]d = + 16 ( c = 1 , chcl3 ) . following the 
 general glycosylation procedure , 
 donor 8a ( 50 mg , 0.10 mmol ) and acceptor 3 ( 50 mg
, 0.08 mmol ) afforded the following purification by column 
 chromatography ( hexane : etoac 5:1 to 4:1 ) : 11a as colorless 
 oil ( 28 mg , 40% ) .
donor 8b ( 50 mg , 0.10 mmol ) and acceptor 3 ( 40 mg , 
 0.08 mmol ) afforded the following purification by column chromatography 
 ( hexane : etoac 5:1 to 4:1 ) : 11b as colorless oil ( 66 mg , 
 81% ) .
donor 8c ( 50 mg , 0.10 mmol ) and acceptor 6k ( 30 mg , 0.08 mmol ) 
 afforded the following purification by column chromatography ( hexane : etoac 
 5:1 to 4:1 ) : 11c as colorless oil ( 60 mg , 82% ) : h nmr ( 400 mhz , cdcl3 )  : 7.507.44 
 ( 2h , m , ph ) , 7.417.31 ( 5h , m , ph ) , 7.257.20 ( 3h , m , 
 ph ) , 5.53 ( 1h , s , phcho2 ) , 5.09 ( 1h , d , j = 3.3 hz , h-1 ) , 4.99 ( 1h , d , j = 3.3 hz , h-1 ) , 4.88 ( 1h , d , j = 11.7 hz , ochhph ) , 4.78 ( 1h , d , j = 11.7 hz , ochhph ) , 4.29 ( 1h , dd , j = 9.9 , 4.5 hz , chh ) , 4.13 ( 1h , ddd , j = 11.3 , 8.3 , 5.3 
 hz , h-3 ) , 4.074.01 ( 1h , m , chh ) , 
 3.94 ( 1h , dd , j = 9.4 , 3.4 hz , h-2 ) , 3.92 ( 1h , dd , j = 9.4 , 8.9 hz , h-3 ) , 3.873.75 ( 3h , m , h-5 , h-5 , 
 chh ) , 3.71 ( 1h , t , j = 10.1 hz , 
 chh ) , 3.61 ( 1h , t , j = 9.1 hz , h-4 ) , 
 3.51 ( 1h , dd , j = 9.2 , 8.4 hz , h-4 ) , 3.43 
 ( 3h , s , och3 ) , 2.25 ( 1h , app dd , j = 13.2 , 
 5.1 hz , h-2a ) , 1.73 ( 1h , ddd , j = 13.5 , 11.4 , 
 3.7 hz , h-2b ) , 1.170.86 ( 49h , m , 7 x sich(ch3)2 ) ; c nmr 
 ( 101 mhz , cdcl3 )  : 139.0 ( 4 c ) , 137.6 ( 4 c ) , 
 129.0 ( ch ) , 128.28 ( ch ) , 128.25 ( ch ) , 127.7 ( ch ) , 127.4 ( ch ) , 126.2 
 ( ch ) , 101.5 ( phcho2 ) , 97.4 ( c-1 ) , 92.9 
 ( c-1 ) , 81.5 ( h-4 ) , 77.3 ( c-3 ) , 75.2 ( phch2o ) , 74.7 ( c-4 ) , 73.7 ( ch ) , 73.5 ( c-2 ) , 71.9 ( c-3 ) , 
 69.2 , 63.5 ( c-6 , c-6 ) , 62.6 ( ch ) , 55.3 ( och3 ) , 
 38.0 ( c-2 ) , 18.24 ( si(ch(ch3)2 ) ) , 18.20 ( si(ch(ch3)2 ) ) , 18.15 ( si(ch(ch3)2 ) ) , 
 17.7 ( si(ch(ch3)2 ) ) , 17.6 ( si(ch(ch3)2))0 , 17.59 ( si(ch(ch3)2 ) ) , 17.53 ( si(ch(ch3)2 ) ) , 17.48 ( si(ch(ch3)2 ) ) , 17.45 ( si(ch(ch3)2 ) ) , 17.4 ( si(ch(ch3)2 ) ) , 13.1 ( si(ch(ch3)2 ) ) , 12.5 
 ( si(ch(ch3)2 ) ) , 12.4 ( si(ch(ch3)2 ) ) , 12.2 ( si(ch(ch3)2 ) ) , 12.2 ( si(ch(ch3)2 ) ) .
maldi - hrms for c48h80nao11si3 ( mna ) calcd : 
 939.4869 ; found : 939.4896 .
[ ]d22 = + 51 ( c = 0.0030 , chcl3 ) . following the general 
 glycosylation procedure , donor 9 ( 50 mg , 0.13 mmol ) and 
 acceptor 3 ( 52 mg , 0.11 mmol ) afforded the following 
 purification by column chromatography ( hexane : etoac , 8:1 to 4:1 ) 12 as a colorless oil ( 78 mg , 74% , : = 9:1 ) . 
 spectroscopic data in agreement with literature .
following the general 
 procedure , donor 9 ( 50 mg , 1.3 mmol ) and acceptor 6k ( 42 mg , 1.1 mmol ) afforded the following purification by 
 column chromatography ( hexane : etoac 20:1 to 10:1 ) : 12b as colorless oil ( 72 mg , 87% , : = 10:1 ) : h nmr ( 400 mhz , cdcl3 )  : 7.527.48 ( 2h , 
 m , ph ) , 7.407.25 ( 8h , m , ph ) , 5.58 ( 1h , s , phcho2 -anomer ) , 5.56 ( 1h , s , phcho2 -anomer ) , 5.07 ( 1h , d , j = 
 3.9 hz , h-1 ) , 4.884.84 ( 2h , m , h-1 , ochhph ) , 4.78 ( 1h , d , j = 11.4 hz , ochhph ) , 4.30 ( 1h , dd , j = 9.9 , 4.5 hz , h-6a ) , 4.07 
 ( 1h , ddd , j = 11.3 , 8.3 , 5.3 hz , h-3 ) , 3.97 
 ( 1h , t , j = 9.3 , h-5 ) , 3.893.72 ( 3h , 
 m , h-4 , h-5 , h-6b ) , 3.693.60 ( 2h , m , h-2 , 
 h-3 ) , 3.45 ( 1h , s , och3 -anomer ) , 3.45 ( 1h , s , och3 -anomer ) , 3.27 ( 1h , j = 8.7 hz ,
h-4 ) 
 ( 2.24 ( 1h , app dd , j = 13.2 , 5.1 hz , h-2a ) , 
 1.74 ( 1h , ddd , j = 13.5 , 11.4 , 3.7 hz , h-2b ) , 
 1.29 ( 3h , d , j = 6.3 hz , ch3 ) 1.141.02 
 ( 28h , m , 4  sich(ch3)2 ) ; c nmr ( 101 mhz , cdcl3 )  : 
 138.66 ( 4 c ) , 137.42 ( 4 c ) , 128.89 ( ch ) , 128.28 ( ch ) , 
 128.19 ( ch ) , 127.7 ( ch ) , 127.57 ( ch ) , 126.0 ( ch ) , 101.25 ( phcho2 ) , 100.6 ( c-1 ) , 100.25 ( c-1 ) , 82.0 
 ( c-2 ) , 80.37 ( c-3 ) , 79.99 ( c-4 ) , 77.94 ( c-5 ) , 75.25 ( phch2o ) , 71.22 ( c-3 ) , 69.07 ( c-6 ) , 68.3(c-5 ) , 
 62.23 ( c-4 ) , 55.2 ( och3 ) , 38.67 ( c-2 ) , 29.7 ( ch3 ) , 
 18.1412.27 ( 4  si(ch(ch3)2 ) ) .
esi - hrms for c39h60nao10 ( mna ) calcd : 767.3623 ; found : 
 767.4002 .
[ ]d = + 25 ( c = 1 , chcl3 ) . [ ]d22 = + 32 ( c = 1 , chcl3 ) . following general 
 procedure , donor 2a ( 50 mg , 0.12 mmol ) , acceptor 6d
( 58 mg , 0.0998 mmol ) , and a solution mixture , prepared 
 containing chiral acid ( 0.012 mmol ) and thiourea ( 0.012 
 mmol ) in anhydrous dcm ( 1 ml ) , were mixed together .
after 2 h , the disaccharide formation 
 was determined to be complete by tlc .
the reaction mixture was then 
 cooled to 0 c , and molecular sieves 4  were added
. once 
 cooled , a solution of 1,2:3,4-di - o - isopropylidene--d - galactopyranoside 6c ( 26 mg , 0.0998 mmol ) in 
 anhydrous dcm ( 0.5 ml ) was added followed by addition of nis ( 45 mg , 
 0.2 mmol ) and finally the dropwise addition of a solution of tmsotf 
 ( 95 l , 40 l in 20 ml anhydrous dcm , 0.001 mmol ) .
after 
 1 h , the reaction was determined to be complete and was quenched with 
 et3n ( 0.1 ml ) , diluted with dcm ( 25 ml ) , washed with na2s2o3 ( sat .
( 25 ml ) , brine ( 25 ml ) , 
 dried over mgso4 , and concentrated in vacuo .
purification by column chromatography ( hexane : etoac , 10:1 to 3:1 ) 
 afforded product 13 as a white solid ( 59 mg , 51% ) .
spectroscopic 
 data in agreement with literature . following the general 
 glycosylation procedure , 
 donor 14 ( 50 mg , 0.12 mmol ) and acceptor 3 ( 46 mg , 0.10 mmol ) afforded the following purification by column 
 chromatography ( hexane : etoac 20:1 to 12:1 ) : 15 as a yellow 
 oil ( 72 mg 83% ) : h nmr ( 500 mhz ; cdcl3 )  
 7.407.21 ( m , 30h , ar 
h ) , 5.04 ( 1h , d , j = 1.3 hz , h-1 ) , 5.00 ( 1h , d , j = 10.8 hz , 
 ochhph ) , 4.93 ( 1h , d , j = 11.6 hz , 
 ochhph ) , 4.86 ( 1h , d , j = 10.9 hz , 
 ochhph ) , 4.834.78 ( 2h , m , ochhph ) , 4.69 ( 1h , d , j = 12.2 hz , ochhph ) , 4.62 ( 1h , d , j = 2.7 hz , h-1 ) , 4.61 ( 1h , d , j = 5.4 hz , ochhph ) , 4.58 ( 2h , s , ochhph ) , 4.54 ( 1h , d , j = 10.8 hz , ochhph ) , 4.42 ( 1h , d , j = 11.8 hz , ochhph ) , 4.35 ( 1h , d , j = 11.8 hz , ochhph ) , 4.043.96 ( 1h , t , j = 9.3 
 hz , h-3 ) , 3.89 ( 3h , t , j = 3.1 hz , h-3 , h-4 , 
 h-5 ) , 3.83 ( 1h , dd , j = 11.4 , 4.7 hz , h-6a ) , 
 3.74 ( 1h , ddd , j = 10.0 , 4.6 , 1.8 hz , h-5 ) , 3.63 
 ( 1h , dd , j = 11.4 , 1.9 hz , h-6b ) , 3.583.54 
 ( 2h , m , h-6a , h-2 ) , 3.543.51 ( 1h , m , h-6b ) , 3.48 ( 1h , dd , j = 10.1 , 8.9 hz , h-4 ) , 3.33 ( 3h , s , och3 ) , 2.031.99 
 ( 1h , m , h-2 ) .
c nmr ( 126 mhz , cdcl3 )  138.9 ( 4 c ) , 138.7 ( 4 c ) , 138.4 ( 4 c ) , 
 138.3 ( 4 c ) , 138.16 ( 4 c ) , 138.1 ( 4 c ) , 128.41 ( ch ) , 
 128.2 ( ch ) , 127.7 ( ch ) , 98.3 ( c-1 ) , 97.9 ( c-1 ) , 82.1 ( c-3 ) , 
 80.0 ( c-2 ) , 77.9 ( c-4 ) , 75.8 ( ch2ph ) , 
 74.9 ( ch2ph ) , 74.3 ( ch2ph ) , 74.16 ( c-3 ) , 73.3 ( ch2ph ) , 73.3 ( ch2ph ) , 72.9 ( c-4 ) , 
 70.2 ( ch2ph ) , 70.1 ( ch2ph ) , ( c-5 ) , 69.8 ( c-5 ) , 69.4 ( c-6 ) , 
 66.0 ( c-6 ) , 55.0 ( och3 ) , 29.7 ( c-2 ) .
esi - hrms for 
 c55h59dnao10 ( mna ) calcd : 904.4147 ; found : 904.4142 .
 a practical approach for the -stereoselective 
 synthesis 
 of deoxyglycosides using cooperative brnsted acid - type organocatalysis 
 has been developed . 
 the method is tolerant of a wide range of glycoside 
 donors and acceptors , and its versatility is exemplified in the one - pot 
 synthesis of a trisaccharide . 
 mechanistic studies suggest that thiourea - induced 
 acid amplification of the chiral acid via h - bonding is key for the 
 enhancement in reaction rate and yield , while stereocontrol is dependent 
 on the chirality of the acid . 
Introduction
Results and Discussion
Conclusions
Experimental Section