Stereoselective synthesis of unnatural spiroisoxazolinoproline-based amino acids and derivatives
A route to spiroisoxazolinoproline-based amino acid derivatives is reported in which exomethyleneprolinate 4 (tert-butyl ester) reacts as a dipolarophile with nitrile oxides to generate spiroisoxazolinoprolinates 7/10/11 in good yields (70-75%) and with ca. 1:4 cis:trans diastereoselectivity. tert-Butyl spiroisoxazolinoprolinates were separable by column chromatography and amenable to scale-up leading to single diastereoisomers of N-Boc and N-Fmoc protected spiroisoxazolinoproline amino acids.
Cheng, Wei-Chieh,Liu, Yannan,Wong, Melissa,Olmstead, Marilyn M.,Lam, Kit S.,Kurth, Mark J.
p. 5673 - 5677
(2007/10/03)
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