(S)-6-((S)-3-amino-4-hydroxy-butyl)-6-aza-spiro[2.5]octan-4-ol → (3S,6S)-3-[2-((S)-4-Hydroxy-6-aza-spiro[2.5]oct-6-yl)-ethyl]-6-methyl-5-oxo-hexahydro-oxazolo[3,2-a]pyrazine-7-carboxylic acid benzyl ester

Participants

Reaction Steps

A solution of (S)-2-[benzyloxycarbonyl-(2-oxo-ethyl)-amino]-propionic acid methyl ester (intermediate 1; 570 mg, 2.04 mmol) and (S)-6-((S)-3-amino-4-hydroxy-butyl)-6-aza-spiro[2.5]octan-4-ol (445 mg, 2.04 mmol) in toluene (6 mL) was heated at reflux for 16 h, then the reaction mixture was concentrated. Chromatography (SiO2; DCM→DCM/MeOH/25% aq. ammonia solution 90:10:0.25) produced the title compound (763 mg, 84%) as a 70:30 mixture of (R)- and (S)-epimers. White foam, MS (ISP)=446.2 (M+H)+.

Provenance & Evidence