ASYMMETRIC SYNTHESIS VIA ACETAL TEMPLATES. 12. HIGHLY DIASTEREOSELECTIVE COUPLING REACTIONS WITH A KETENE ACETAL. AN EFFICIENT, ASYMMETRIC SYNTHESIS OF R-(+)-α-LIPOIC ACID.

Article abstract of DOI:10.1016/S0040-4039(00)98830-0

TiCl4 catalyzes the essentially quantitative coupling of chiral acetals 1 with 1-t-butoxy-1-t-butyldimethylsilyloxyethene 2 to generate β-alkoxycarboxylates in wich the new asymmetric center is formed with excellent diastereoselection. β-Hydrocarboxylic acids of high ee result from removal of the chiral auxiliary.The procedure has been appllied to the synthesis of R-(+)-α-lipoic acid 10.