The acyl substituent in {HEAD ~ the 10 position} may also be substituted with electron donating groups so long as the acyl substituent is {TAIL ~ electron} withdrawing overall 
The acyl substituent in { HEAD ~ the 10 position } may also be substituted with electron donating groups so long as the acyl substituent is { TAIL ~ electron } withdrawing overall
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH