pristinamycin iib pristinamycin iib pristinamycin iib is an antibiotic of the streptogramin a class. it was isolated from streptomyces pristinaespiralis and its chemical structure was first determined in 1966. pristinamycin iib names other names (27r)-26,27-dihydrovirginiamycin m1; ostreogrycin g; virginiamycin m2; volpristin identifiers cas number 21102-49-8 y 3d model (jsmol) interactive image chemspider 4952854 echa infocard 100.132.888 pubchem cid 6450239 unii 18uan5144e y comptox dashboard (epa) dtxsid10864978 inchi inchi=1s/c28h37n3o7/c1-17(2)26-19(4)7-8-24(34)29-10-5-6-18(3)12-21(32)13-22(33)14-25-30-23(16-37-25)27(35)31-11-9-20(15-31)28(36)38-26/h5-8,12,16-17,19-21,26,32h,9-11,13-15h2,1-4h3,(h,29,34)/b6-5+,8-7+,18-12+/t19-,20+,21-,26-/m1/s1key: wmkfeqgqmbsgsa-txzfevtpsa-n smiles o(/c=c(c)/c=c/cnc(/c=c/(c)(oc1=o)c(c)c)=o)cc(cc2=nc(c(n31ccc3)=o)=co2)=o properties chemical formula c28h37n3o7 molar mass 527.618 g·mol−1 except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). infobox references