Conversion of 2, 5-Diphenyl- and 2, 5-Dibenzyl-pyrazines to 2, 5-Diketopiperazines

Abstract

The reactions of 2, 5-diphenyl- (I) and 2, 5-dibenzyl-pyrazine 1-oxides (II) with phosphoryl chloride and acetic anhydride were examined. 2, 5-Dichloro-3, 6-diphenyl- (XI) and 2, 5-dichloro-3, 6-dibenzyl-pyrazines (XIII) were converted to the corresponding 2, 5-diketopiperazines, α-phenylglycine anhydride (XXV) and phenylalanine anhydride (XXVI), respectively. The stereochemistry of the products is discussed. However, attempts to convert 2, 5-dichloro-3, 6-dihydroxymethylpyrazine (XXXIV) to serine anhydride were unsuccessful.