The development of efficient and stereoselective methods to produce 1,4-disubstituted-2-oxopiperazine in enantiomerically pure form, from a readily available starting material is crucial. Herein, we report a reduction modification to our previously described synthesis of 1,4-disubstituted-2-oxopiperazine and also two original shortly accessed pathways. These new pathways can be routinely performed on a multigram scale and should rapidly find a place in the preparation of the 3-substituted-2-oxopiperazine diastereomers. Stereoselective alkylation of 1,4-disubstituted-2-oxopiperazine led to the corresponding (3S)-diastereomer or (3R)-diastereomer from the corresponding 2-oxopiperazine enantiomer with the chiral inductor substituted at the N-1 (1*) position, respectively, in good yield. (C) 2008 Elsevier Ltd. All rights reserved.
Simple, versatile and highly diastereoselective synthesis of 1,3,4-trisubstituted-2-oxopiperazine-containing peptidomimetic precursors
O-deprotection of (1'S)-4-(tert-butoxycarbonyl)-1-[1'-phenylmethyloxymethyl-2'-[(tert-butyldimethyl silyl)oxy]ethyl]-2-oxopiperazine furnished an enantiomerically pure alcohol whose regio- and diastereoselective C3-alkylation yielded either (3R)- or (3S)-1,3,4-trisubstituted-2-oxopiperazines in high diastereomeric purity. These derivatives were efficiently transformed into (1'R)- or (1'S)-peptide templates