Acid-catalysed cyclisation of 2-methyl-2[3-(2,4-dimethoxyphenyl)-5-methoxypent-2-enyl]-cyclopentane-1,3-dione: Structure of a novel product

Yuehchukene analogs

“…N-Sulfonylation of Keto Ester 20b. By the general procedure for the reactions conducted under phase-transfer conditions (vide supra), 295 mg (1 mmol) of indole 20b was induced to react with 190 mg (1 mmol) of p-toluenesulfonyl chloride to give 409 mg (91%) of colorless, crystalline indole 20c: mp 81-82 °C (CH2-C12-C6H14); UV Xmax 206 nm (e 33110), 222 (21380), 267 (8410), 277 (8620), 307 (14 780); IR C=0 1732 (s), 1675 (s), C=C 1601 (m), S02 1370 (s), 1169 (s) cm'1; NMR 1.54 (s, 3, Me), 2.16 (d, 1, H-ll, J = 19.0 Hz), 2.40 (s, 3, aryl Me), 2.49 (dd, 1, H-ll, J = 7.7, 19.0 Hz), 3.19 (t, 1, a-C02 H, J = 2.7 Hz), 3.44 (br d, 1, -keto H, J = 7.7 Hz), 3.51 (s, 3, OMe), 4.07 (d, 1, H-8, J = 6.0 Hz), 5.83 (d, 1, H-9, J = 6.0 Hz), 7.28-8.30 (m, 8, aryl Hs); MS m/e 449 (M+, 67%), 385 (55), 294 (30), 266 (51), 235 (24), 234 NMR 1.63 (s, 3, Me), 2.28 (dd, 1, H-ll, J = 7.0, 19.5 Hz), 2.32 (s, 3, aryl Me), 2.92 (d, 1, H-ll, J = 19.5 Hz), 3.11 (t, 1, a-C02 H, J = 2.9 Hz), 3.29 (m, 1, bridgehead H), 3.43 (s, 3, OMe), 3.78 (d, 1, H-8, J = 6.4 Hz), 4.20 (d, 1, OH, J = 3.5 Hz), 5.62 (dd, 1, OCH, J = 3.5, 7.2 Hz), 5.82 (d, 1, H-9, J = 6.4 Hz), 7.16-8.08 (m, 8, aryl Hs); MS m/e 451 (M+, 5%), 433 (5), 297 (25), 296 (base), 264 (33), 236 (20), 218 (22), 144 (63), 91 (30); exact mass 451.1443, caled for C26H26N05S 451.1452.…”

“…A possibly facile synthesis of the 12,12'-bisdemethyl derivative of yuehchukene was based on the above synthesis of the natural product itself and required the preparation of demethyl-13-(dehydroprenyl) indole ( 10) and its dimerization. The construction of the diene was initiated by the reaction of crotonyl chloride with the Grignard reagent from indole and methylmagnesium bromide3 and led to the desired carbonyl compound 11a, albeit in low yield (21%), and to (5) Despite the pictorialization of the reaction sequence revealing nonconcertedness, the path was called a Diels-Alder reaction by the authors.2 (6) Cf. : Malhotra, S. K.; Hostyneck, J. J.; Lundin, A. F. J.…”