Amino alcohol-derived acyl-transfer

One of the first effective chiral PPY derivatives to be developed for asymmetric acyl transfer was catalyst 7, which was shown by Fuji and Kawabata in 1997 to be effective for the acylative KR of various racemic mono-benzoylated ds-diol derivatives [76]. Subsequently, it was also successfully applied in the KR of N-protected cyclic ds-amino alcohols [77]. Using 5 mol% of PPY 7 in the presence of a stoichiometric amount of collidine in CHCI3 at rt, a variety of cyclic ds-amino alcohol derivatives were resolved with moderate selectivities (s = 10-21) (Table 8.6). 

The utilization of a-amino acids and their derived 6-araino alcohols in asymmetric synthesis has been extensive. A number of procedures have been reported for the reduction of a variety of amino acid derivatives however, the direct reduction of a-am1no acids with borane has proven to be exceptionally convenient for laboratory-scale reactions. These reductions characteristically proceed in high yield with no perceptible racemization. The resulting p-amino alcohols can, in turn, be transformed into oxazolidinones, which have proven to be versatile chiral auxiliaries. Besides the highly diastereoselective aldol addition reactions, enolates of N-acyl oxazolidinones have been used in conjunction with asymmetric alkylations, halogenations, hydroxylations, acylations, and azide transfer processes, all of which proceed with excellent levels of stereoselectivity. 

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