No abstract

A mixture of acetic and sulfuric acids converts haematoporphyrin into a complex mixture of porphyrins of which the main product has been characterized as the diacetate (1g). Other compounds identified in the reaction mixture were the known vinylporphyrins (1b-d), (1h) and (li) and the isomeric monoacetoxyethyl(monohydroxyethyl)porphyrins (11) and (1m). Analysis of the reaction mixture was complicated by the presence of 1'-ethoxyethyl derivatives (1e) or (1f), (1j) and (1k)which presumably arose by solvolysis of the corresponding acetate with ethanol present in the chloroform used for the chromatographic separation.

Melt pyrolysis of the cis-6,7-dimethoxy-2-methyl-1-phenyl-1,2,3,4- tetrahydroisoquinoline N-oxide (2b) afforded the Meisenheimer rearrangement product, 7,8-dimethoxy-3-methyl-1-phenyl-1,3,4,5- tetrahydro-2,3-benzoxazepine (5b), in good yield, as did pyrolysis of the corresponding trans-N-oxide (3b) (in a melt) or a mixture of (2b) and (3b) (melt or in solution). The synthesis of the 1-deuterated analogue, (5c), of (5b) is described, together with products derived from (5b) by cleavage of the N-O bond which were used to confirm its structure. Meisenheimer rearrangement of the N-oxides (10) and (11) of 6,7-dimethoxy-1-(3,4-dimethoxyphenyl)-2-methyl-1,2,3,4-tetrahydroisoquinoline and 2-methyl-1-phenyl-1,2,3,4- tetrahydroisoquinoline gave the analogous 2,3-benzoxazepine derivatives (12) and (13), respectively.

The 13C n.m.r, spectra of the 15 isomeric protoporphyrin dimethyl esters have been determined. Measurements were made on the zinc chelate derivatives of the porphyrins in the presence of pyrrolidine and assignments are given for the side chain and methine carbon atoms.