SYNTHESIS AND DIELS-ALDER REACTION OF 5-BETA-METHYL-BETA-DIHYDROTHEBAINE AND ITS 6-DEMETHOXY ANALOG (CHEMISTRY OF OPIUM-ALKALOIDS .42.)

The scission of the 4,5 alpha-epoxy bridge of 5 beta-methylthebaine (2 ) and 5 beta-methyl-6-demethoxythebaine (5), yielded 5 beta-methyl-bet a-dihydrothebaine (4) and 5 beta-methyl-6-demethoxy-beta-dihydrothebai ne (6), respectively. The scission was carried out by zinc reduction i n a potassium hydroxide solution. It took place with retention of the 6,8-diene system and the configuration at the C-5 atom. To perform the Diels-Alder reaction on 4, the hydroxyl substituent at C-4 had to be protected with a phenyl group, yielding 5 beta-methyl-4-O-phenyl-beta- dihydrothebaine (7). The Diels-Alder reaction of 7 was carried out in boiling ethyl propenoate for three weeks. Two 6 beta,14 beta-ethenomor phinans (8 and 9) were obtained. For the Diels-Alder reaction of 6 no protection of the hydroxyl substituent at C-4 was necessary. Cycloaddi tion gave after one day two 6 beta,14 beta-ethenomorphinans (10 and 11 ).