The allylboration of ℓ-amino ketones

A series of unsaturated α,β-amino alcohols were prepared via allylboration of the corresponding N-protected α-amino ketones. This new methodology is a potentially useful method for the diastereoselective preparation of a wide variety of acyclic synthetic building blocks. Treatment of an N-protected α-amino carbonyl with one equivalent of an allylboron reagent provides the corresponding diastereomeric unsaturated α,β-amino alcohols. The diastereoselectivity is not dramatically affected by the electronic nature of the N-protecting group. However, the diastereomeric excess is noticeably reduced when Lewis basic solvents are used. Reaction temperature exerts a minor, but discernible, influence on the stereochemical outcome of the allylboration. This allylboration methodology can easily be incorporated into complex syntheses of biologically important molecules containing α,β-amino alcohol subunits.