Synthetic studies on 8-deoxyserratinine type alkaloids. Selective cyclization of the 1,2-cyclohexanediacetaldehyde derivative by intramolecular aldol condensation.
1980; Pharmaceutical Society of Japan; Volume: 28; Issue: 4 Linguagem: Inglês
10.1248/cpb.28.1276
ISSN1347-5223
AutoresTakashi Harayama, Muneo Takatani, Yasuo Inubushi,
Tópico(s)Synthesis and bioactivity of alkaloids
ResumoIn connection with the synthesis of 8-deoxyserratinine type alkaloids, the regioselective cyclization reaction of the 1, 2-cyclohexanediacetaldehyde derivative (6) by intramolecular aldol condensation was investigated. The acetal (5) was stereoselectively prepared by two routes using the Diels-Alder reaction. The first route involved the Diels-Alder reaction of the dienophile (12), obtained from 8 via 9, 10 and 11, with butadiene in the presence of 0.5 eq. AlCl3 and acetalization of the adduct (13) to give 5 in 8% yield from 8. The second route involved conversion of the adduct (15), obtained by the Diels-Alder reaction of 8 with butadiene in the presence of 0.5 eq. BF3·Et2O, into 5 [22% yield based on the consumed dienophile (8)] via 16 and 17. The dialdehyde (6) was obtained from the cis-decalone derivative (5) via 18. Cyclization of 6 using excess morpholine-camphoric acid in dry Et2O-HMPA and subsequent treatment with (EtO)2POCH2CN gave 21, which was suitable for our purpose, and 22 in a 25 : 1 ratio.
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