Preparations, solution conformations and molecular structures of N,N′‐ethylene‐bridged dipeptides and their derivatives

The solution conformations of novel dipeptides, methyl (2S, 3'S)-3-methyl-2-(2'-oxo-3'-isopropyl-1'-piperazinyl)-butanoate (EVV-OCH3), methyl (2S, 3'S)-3-phenyl-2-(2'-oxo-3'-benzyl-1'-piperazinyl) propionate (EFF-OCH3), and their derivatives (Boc-Gly-EVV-OH, Boc-Gly-EVV-Gly-OH, and Boc-Gly-EFF-OH), were studied by 1H NMR measurements and molecular mechanics calculations (1). The molecular structures of Boc-Gly-EVV-OH, Boc-Gly-EFF-OH, and the hydrochloride of EVV-OCH3 were determined by X-ray analyses. The conformations of the piperazinone rings and the side chains of these oligopeptides were clarified.