Stereodivergent synthesis of diastereoisomeric carba analogs of glycal‐derived vinyl epoxides: A new access to carbasugars

A convenient method for the stereoselective synthesis of diasteroisomeric vinyl epoxides (−)‐ 2α and (−)‐ 2β , the carba analogs of D ‐galactal and D ‐allal‐derived vinyl epoxides 1α and 1β , has been elaborated starting from tri‐ O ‐acetyl‐ D ‐glucal. The key step of this synthesis is an application of the known Claisen thermal rearrangement of a glucal derivative, the vinyl allyl ether (+)‐ 3b , which allows to switch the glycal structure into the corresponding carba analog scaffold. Epoxides (−)‐ 2α and (−)‐ 2β derive from the same synthetic intermediate, the trans diol (+)‐ 5 . Chirality, 2011. © 2011 Wiley‐Liss, Inc.