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The asymmetric aldol reaction of heteroatom-substituted ketene silyl acetals with achiral aldehydes has been developed by the promotion of tin(II) triflate coordinated with a chiral diamine to afford the corresponding aldols having chiral tertiary alcohols at the α-positions. This reaction has been successfully applied to the construction of the basic skeletons of buergerinins F and G starting from achiral materials. (+)-Buergerinin G, a potentially antiphlogistic and febrifuge agent having a unique trioxatricyclo[5.3.1.0 1,5 ]undecane skeleton, is stereoselectively prepared by means of the enantioselective aldol reactions via ten linear steps from crotonaldehyde in 18% overall yield including an effective intramolecular Wacker-type ketalization of the dihydroxy-γ-lactone as a key step. In addition to the former establishment for the synthesis of (+)-buergerinin F, effective divergent methods for the preparation of buergerinins F and G were developed through a unified optically active aldol-type intermediate, which was generated from the tetrasubstituted ketene silyl acetal with crotonaldehyde by the asymmetric Mukaiyama aldol reaction.

Various carboxamides or peptides were synthesized from the corresponding carboxylic acids and amines or alpha-amino acids in high yields by the catalysis of 4-(dimethylamino)pyridine N-oxide (DMAPO) with 2-methyl-6-nitrobenzoic anhydride (MNBA). Because the segment-coupling reaction of alpha-amino acids proceeds through the effective activation of the carboxylic acid moieties with DMAPO in the presence of tertiary amines under mild conditions, undesired racemization was hardly observed in the synthesis of oligopeptides such as Z-Gly-Phe-Val-OMe, Z-Phe-Val-Ala-OMe, and Bz-Val-Val-OMe.