Meerwein-Ponndorf-Verley-type reduction of N-tosylsilylimines with chiral lithium amide 2 affords alpha-silylamines in high enantioselectivity. Since the enantioselectivity observed was inconsistent with our previously proposed chairlike six-membered transition structure, we performed density functional theory (DFT) calculations on transition states leading to (S)- and (R)-7a and (S)- and (R)-7e using an N-phenylsulfonyl derivatives 12 and 13 as model systems. Results of the calculations showed that the structures are considerably deformed from the chairlike form with steric repulsions between the 1'-methylene group and the imine-carbon substituents playing an important role in the control of the, enantioselectivity.
The stereoselective total synthesis of the marine alkaloid, (−)-amathaspiramide F (1), was achieved from the α-hydroxy-α-ethynylsilane 2. The key steps involved in the synthesis were (1) the enolate Claisenrearrangement of the α-acyloxy-α-alkenylsilane for the stereoselectiveconstruction of the consecutive C5 and C9 chiral centers of 1 (erythro configuration), (2) the construction of aza-spirohemiaminal