Stereoselective Ene Reaction of Allylsilanes With Amino Aldehydes - An Application To the Synthesis of Potential Hiv-1 Protease Inhibitors

2-Substituted 3-(trimethylsilyl)-1-propenes react with N-Boc-alpha-amino aldehydes in the presence of BF3.OEt(2) to give homoallylic alcohols, potential intermediates for the synthesis of hydroxyethylene peptide isosteres. The reaction gives a predominance of the syn products, but 2-(chloromethyl)-3-(trimethylsilyl)-1-propene (5) exhibits a higher stereoselectivity with respect to other analogous allylsilanes. We hypothesize that this selectivity is due to an ''ene'' reaction followed by desilylation in the reaction medium (BF3.OEt(2), CHCl3). This reaction shows applicability to the synthesis of potential HIV-1 protease inhibitors. The preparation of compound 3, which has a structure related to the potent inhibitor L-682,679, is described.