Synthetic Studies on d-Biotin, Part 9. An Improved Asymmetric Synthetic Route to d-Biotin via Hoffmann-Roche Lactone-Thiolactone Approach

An efficient and highly stereoselective total synthesis of d-biotin has been achieved starting from cis-1,3-dibenzyl-2-imidazolidone-4,5-dicarboxylic acid (2) with an overall yield of 33%. Polymer-supported oxazaborolidine-catalyzed asymmetric reduction of meso-cyclic imide 4 constitutes the key synthetic step in introducing stereogenic centers into the d-biotin molecule.