2,6-Lutidine → t-butyl (RS)-2-chloro-2-((3R,4R)-3-phenylacetamido-4-[(RS)-tetrahydropyran-2-ylcarbonylmethylthio]azetidin-2-on-1-yl]acetate

Participants

Reaction Steps

t-Butyl 2-hydroxy-2-[(3R,4R)-3-phenylacetamido-4-[(RS)-tetrahydropyran-2-ylcarbonylmethylthio]azetidin-2-on-1-yl]acetate (1.9g) in dry THF (10ml) was treated with 2,6-lutidine (0.62g, 0.67ml) followed by thionyl chloride (0.69g, 0.42ml) in THF (5ml) dropwise at <-20° C. under argon. The reaction mixture was allowed to warm slowly to ca 0° C. at which point no starting material was observed by t.l.c. (ethyl acetate). The reaction mixture was filtered and solvent removed in vacuo, the residue dissolved in toluene and evaporated to afford crude t-butyl (RS)-2-chloro-2-((3R,4R)-3-phenylacetamido-4-[(RS)-tetrahydropyran-2-ylcarbonylmethylthio]azetidin-2-on-1-yl]acetate as a brown gum. This was dissolved in dry dioxan (10ml) and treated with tri-n-butylphosphine (1.79g, 2.2ml). The reaction mixture was stirred until loss of starting material was observed by t.l.c. (ethyl acetate) ca 0.5h. After removal of solvent in vacuo the title compound was obtained by flash chromatography (eluting with 50,60,80% ethyl acetate in hexane, ethyl acetate) as a pale brown foam (1.95g, 75%); vmax (CH2Cl2) 3417(w), 1762, 1681, 1625cm-1. [Mass spectrum +ve ion (thioglycerol) MH+ (677)].

Provenance & Evidence