We aimed to synthesize ten-membered lactams ring-closed at C-4 of the indole by photocyclization reaction of γ-chlorotiglyl L-tryptophan methyl ester 5a for structure-activity study of medium-ring lactams related to indolactams having tumor-promoting activity. However, the 13C-NMR spectra of the products showed that two eight-membered lactams ring-closed at C-4 of the indole, (4S, 7S)-1, 3, 4, 5, 6, 7-hexahydro-4-methoxycarbonyl-7-methyl-6-oxo-7-vinylazocino[4, 5, 6-cd]indole (6a) and its (4S, 7R)-epimer 7a, and a seven-membered lactam ring-closed at C-2 of the indole, (2S, 5S)-1, 2, 3, 4, 5, 6-hexahydro-2-methoxycarbonyl-5-methyl-4-oxo-5-vinylazepino[4, 5-b]indole (8a), were produced rather than the expected ten-membered lactams 3a and 4a. That is, this photocyclization linked the carbon atom adjacent to the amide-carbonyl groups to the indole ring.
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