30. Colchicine and related compounds. Part IX

Benzoannellated Fenestranes Bearing para‐Terphenyl Units

“…To this end, two approaches were investigated. In the first one, we started from the 1,5-(2diphenylyl)pentadienone 23, which was synthesized from 2phenylbenzaldehyde, 22, [53] and acetone in 64 % yield (Scheme 5). Twofold Michael addition with diphenylindanedione 7 in glacial acetic acid gave a mixture of the trans-and cis-diarylspirotriketones 24 and 25 in 54 % combined yield.…”

Biosynthesis. Part 26. Synthetic studies on structural modification of late biosynthetic precursors for colchicine

“…(i) Introduction of a C-2 unit by acylation or alkylation at the nitrogen atom to give (19); (ii) deprotection of the phenolic group; and (iii) base-catalysed ringclosure onto ring c of (19) involving aryl-[l,6]-participat ion.I6 Condensation of 3,4,5-trimethoxybenzaldehyde with 3benzyloxy-4-methoxyphenylacetic acid (20) under Perkin conditions '* afforded a 55-60% yield of the Z-a-carboxystilbene (21) (Scheme 4) which was converted into its methyl ester (22); the 2-stereochemistry from such condensations has been rationalised.'' Oxidative closure of the stilbene (22) to the phenanthrene (23) was effected by photolysis 2o in the presence of iodine. The ester grouping conjugated with the stilbene double bond markedly slowed the reaction rate so that irradiation for 70 h was necessary to give a reproducible yield (25%) of the phenanthrene (23).…”

“…)-1 -metho.~.vcarbo1r~~l-2-( 3,4,5-trimethoxyp heny1)ethene (22) .-The foregoing acid (2 1 ) (5 g) was heated at reflux in methanol (100 ml) with concentrated sulphuric acid (4 ml) for 2 h; the mixture was then cooled to 0 "C. The resultant crystals were collected and washed with cold solvent to give the methyl ester (4.75 g, 92%), m.p. 129-130 "C (from methanol) (Found: C, 69.8; H, 5.8.…”

“…2-Acetyl-4-benzyloxy-2'-formyl-4', 5,5 ',6'-tetramethoxybiphenyl (28).-The preceding diol (27) (1.25 g, 2.75 mmol) in dry benzene (40 ml) was stirred at 20 "C for 1 h with lead(1v) acetate 22 (1.25 g). The suspension was filtered (Celite) and the collected precipitate was washed with benzene (20 ml); the combined organic solutions were then washed with water (3 x 50 ml).…”

A facile synthesis of dibenzopyrroloazepinones as tetracyclic allocolchicinoids—an unusual 1,2-phenyl shift

“…A previously reported attempt to form the acid chlorides of related 2 0 -methoxybiphenyl acids with thionyl chloride had resulted in the exclusive formation of benzo[c]chromen-6-ones. 7 Indeed, we found that our standard method of using oxalyl chloride with the addition of a small (1-2 drops) catalytic quantity of DMF gave up to 35% formation of the benzo[c]chromen-6-ones. However, it was found that the formation of this by-product could be minimised by more rapid formation of the acid chlorides using a larger quantity of DMF (5 drops) to give the amides 3c-h in high yield (66-100%).…”