In order to examine the total syntheses of ochotensine (1) and ochotensimine (II), one of the isomers, iso‐ochotensine (III), was synthesized as a preliminary experiment. Namely, Wittig reaction of VI, followed by treatment with sodium bicarbonate solution, gave the expected compound, 7‐ethoxycarbonyl‐3‐ethoxycarbonyloxy‐2‐methoxy‐13‐methyIene‐10,11‐methyIene‐dioxyochotensinan (VII) which was reduced with lithium aluminum hydride to give III. This was also obtained by methylation of 3‐hydroxy‐2‐methoxy‐13‐methylene‐10,11‐methyIenedioxy‐ochotensinan (VIII).
The synthesis of 1,2,3,4‐tetrahydroazepine[3,2,1‐kl]phenothiazin‐4‐one was accomplished by cyclization of phenothiazine‐10‐butanoic acid using phosphorus pentoxide and absolute ethanol. The title compound represents the first reported example of the azepino[3,2,1‐kl]phenothiazine ring system. A vastly improved malonic ester‐type synthesis of the precursor acid has also been developed.
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