In order to modify and improve the reduction of bicyclic piperazinediones t
o yield enantiomerically pure piperazine derivatives the preparation and re
duction of the corresponding thiolactams were investigated. With a reduced
amount of Lawesson reagent the bicyclic piperazinediones reacted predominan
tly at the C-5 carbonyl moiety to provide C-5 monothiolactams. (C) 2001 Els
evier Science Ltd. All rights reserved.