Racemization of α‐Alkyl‐β‐Keto Esters and Enantioselective Total Synthesis of Two C‐2′′′Epimers of Plant Glycerolipid Santinol C

It is broadly believed that optically active α‐alkyl‐β‐keto esters racemize very quickly. Nevertheless, no one really knows how fast the racemization is. In fact, such species are hardly attainable to date. Now, a facile entry to these greatly understudied esters has been found and their racemization has been studied for the first time. The results showed that under neutral or slightly acidic conditions such species were much more stable than one might expect, though they did racemize rapidly under basic conditions. In light of the new findings, santinol C was also synthesized in enantiopure forms. Probably to everyone's surprise, racemization of such optically active methine groups is not as fast as broadly presumed, especially under slightly acidic or neutral conditions. These previously hardly attainable species, including structurally complex ones such as santinol C, now can be readily accessed using Dess–Martin oxidation of the corresponding aldol as the final step of the synthesis along with specially designed convenient isolation protocol.