syntheses of 2 have been accomplished by highly diastereoselective aldol-type reactions which employ a boron enolate of the chiral oxazolidone 4 (coupled with zinc bromide) 2* and tin (I1) enolates of the chiral thiazolidinethione and the achiral oxazolidinethione 6.2 c We now report that the utilization of the tin (I1) enolate of the simple achiral ketone 74 provides a remarkably high diastereoselectivity to afford the key precursor 2 in 295% ...
