A NEW SYNTHESIS OF COPRINE AND O-ETHYLCOPRINE

Coprine (1), a toxine of the mushroom Coprinus atramentarius, was synthesized starting from the 2-amino- and 1-carboxy-protected L-glutamic acids 4 and 12. Compound 4 was first decarboxylated by a radical chain reaction to bromide 5 which underwent ring closure to cyclopropanecarboxylate 6 on treatment with NaH (Scheme 1). Subsequent oxidative electrolysis of 7 to form tert-butyl N-(1-ethoxycyclopropyl)carbamate (8) and acidic hydrolysis yielded the 1-aminocyclopropanol hydrochloride (9). Selective cleavage of thc amino-protecting group of 8 (--> 10 or 11), coupling of the corresponding amine 13 with L-glutamic acid 12, and acidic hydrolysis of the resulting L-glutamine derivative 17 yielded O-ethylcoprine (3) and coprine (1).