(3S,6S,8aS)-3-[3-((S)-4-hydroxy-6-aza-spiro[2.5]oct-6-yl)-3-oxo-propyl]-6-methyl-5-oxo-hexahydro-oxazolo[3,2-a]pyrazine-7-carboxylic acid benzyl ester → (3S,6S,8aR)-3-[3-((S)-4-Hydroxy-6-aza-spiro[2.5]oct-6-yl)-3-oxo-propyl]-6-methyl-5-oxo-hexahydro-oxazolo[3,2-a]pyrazine-7-carboxylic acid benzyl ester

Participants

Reaction Steps

Condensation of (S)-2-[benzyloxycarbonyl-(2-oxo-ethyl)-amino]-propionic acid methyl ester (intermediate 1) with (S)-4-amino-5-hydroxy-1-((S)-4-hydroxy-6-aza-spiro[2.5]oct-6-yl)-pentan-1-one in analogy with examples 1/2F produced a nearly statistical mixture of the title compound [light brown gum, MS: 472.4 (M+H)+], and its epimer, (3S,6S,8aS)-3-[3-((S)-4-hydroxy-6-aza-spiro[2.5]oct-6-yl)-3-oxo-propyl]-6-methyl-5-oxo-hexahydro-oxazolo[3,2-a]pyrazine-7-carboxylic acid benzyl ester [light brown gum, MS: 472.4 (M+H)|], which were separated by column chromatography (SiO2; DCM→DCM/MeOH/25% aq. ammonia solution 90:10:0.25).

Provenance & Evidence