Key points are not available for this paper at this time.
The reduction of (5 S )-2-amino-5-dibenzylamino-4-oxo-1,6-diphenylhex-2-ene was optimized for diastereoselectivity and overall conversion to (2 S,3 S,5 S )-5-amino-2-dibenzylamino-3-hydroxy-1,6-diphenylhexane ( 2a ). A two-step reduction sequence is described wherein the enamine is reduced with a borane-sulfonate derivative followed by reduction of the resulting ketone with sodium borohydride. The desired 2a was obtained with 84% diastereoselectivity and an acyclic 1,4 stereoinduction ratio of 14:1. This methodology has been used to produce multikilogram quantities of the diamino alcohol core of Ritonavir and should be general to the synthesis of related diamino hydroxyethylene isosteres.
Haight et al. (1999) studied this question.