Synthesis of carba analogs of 6-O-(benzyl)-D-allal- and -D-galactal-derived allyl epoxides and evaluation of the regio- and stereoselective behavior in nucleophilic addition reactions

The new racemic diastereoisomeric epoxides 6 alpha and 6 beta, the carba analogs of the corresponding D-galactal- and D-allal-derived allyl epoxides have been synthesized and their regio- and stereoselective behavior examined in addition reactions with model O-, C-, N-, and S-nucleophiles. The results have indicated that epoxide 6 beta has a pronounced tendency toward anti-1,2-addition, whereas epoxide 6 alpha shows interesting levels of syn- and/or anti-1,4-addition processes. A chiral recognition process found with epoxide 6 beta, turned out to be consistently reduced in epoxide 6 alpha. All the results have been rationalized on the basis of conformational, steric, and stereoelectronic effects. (C) 2011 Elsevier Ltd. All rights reserved.