ACTIVATION OF CARBOXYLIC-ACIDS BY PYROCARBONATES - SYNTHESIS OF ARYLAMIDES OF N-PROTECTED AMINO-ACIDS AND SMALL PEPTIDES USING DIALKYL PYROCARBONATES AS CONDENSING REAGENTS

Activation of carboxylic acids was achieved via dialkyl pyrocarbonates (ROCO)(2)O, (R = ethyl, isopropyl, sec-butyl, tert-butyl) in aprotic solvents in the presence of tertiary amines. A convenient one-pot proc edure for the preparation of arylamides from N-protected amino acids i ncluding arginine and from di-tert-butyl pyrocarbonate in the presence of pyridine (Boc(2)O-pyridine system) was reported. Analogously, diis opropyl, di-sec-butyl or diethyl pyrocarbonate could be used in the pr esence of N-methylmorpholine or triethylamine. A wide variety of N-pro tected amino acid arylamides were prepared in good yields. (C) Munksga ard 1994.