Studies on the syntheses of heterocyclic compounds. Part DLXXVII. An abnormal Hofmann degradation of phenolic berbinium salts

Abstract

Hofmann degradation of 11-hydroxy-10-methoxy-7-methyl-2,3-methylenedioxyberbinium iodide (2) with methanolic potassium hydroxide gave 1,2,3,4-tetrahydro-1-(5-hydroxy-4-methoxy-2-methoxymethylbenzyl)-6,7-methylenedioxy-2-methylisoquinoline (14) in addition to the normal methine base (7). Abnormal Hofmann degradation was observed with schefferine methiodide (3) and nandinine methiodide (4). The mechanism of this type of reaction and the biogenesis of the protoberberine alkaloid mecambridine (22) are discussed.