G. Veinberg, M. Vorona, D. Musel
Apr 1, 1999
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Journal
Journal of Chemical Research
Abstract
The optimal 64 ± 3% yield of pure tert-butyl 6-aminopenicillanate was reached using a 1:1 dioxane-tert-butyl acetate mixture. Attempts to improve the yield by varying the ratio failed (Table 1, entries 4 and 5). Attempts to recover 6-APA by treatment of 3 with trifluoroacetic or Lewis acids in dichloromethane according to procedures published in ref. 4 led to destruction of the fJ-Iactam ring. However 3 proved to be stable under other types of chemical transformations. It was found that, contrary to the benzhydryl protecting group, tert-butyl favored the transformation of 3 into 6-oxopenicillanate 10 in the manner described by Hagiwara et al.S Treatment of 3 in dichloromethane with isopropyl nitrite in the presence of catalytic amounts of trifluoroacetic Scheme 1