Studies of chromenes. Part 9. Syntheses of chromenequinones

Abstract

Syntheses of 2,2-dimethylchromene-5,8-quinone, 2,2-dimethylchromene-6,7-quinone, and 6,7dimethoxy-2,2-dimethylc hromene-5,8 -quinone are described. Being easily bioreduci ble to electronrich chromenes these compounds, and their oxirane derivatives, are of interest as possible anti-tumour alkylating agents.

Bi(OTf)3-catalysed prenylation of electron-rich aryl ethers and phenols with isoprene: a direct route to prenylated derivatives

“…The mild reaction conditions, predictable selectivity and functionality generated makes this reaction a very useful medicinal chemistry tool. The formation of CC and CO bonds in the presence of an inexpensive and easy-to-handle catalyst under 35 mild reaction conditions is also worthy of note. Methyl 3,4,5-trimethoxybenzoate 9, methyl E-3-(3,4,5trimethoxyphenyl)propenoate 11, methyl 3-(3,4,5-trimethoxyphenyl)propanoate 13, methyl E-3-(3,4-dimethoxyphenyl)propenoate 15 and methyl 4-hydroxybenzoate 23 were all synthesised from their corresponding carboxylic acids following the procedure reported by Parrain 43 and gave samples that were consistant with the spectroscopic data reported for 9, 44 11, 43 13, 45 15 46 and 23.…”

“…As previously described, the reaction presumably proceeds via the ortho-prenylated phenol 31a, which undergoes cyclisation under the reaction conditions to afford the chroman 32 (Scheme 4). The dienone 33, resulting from 35 attack at the para-position with respect to the phenol OH, was also isolated from the reaction mixture in 26% yield. Only the chroman 32 was previously reported in the reaction of phenol 30 and isoprene catalysed by using zeolite HSZ-360 17 or Sc(OTf) 3 in ionic liquid.…”

“…19 A similar transformation was, 40 however, observed in the reaction between 3,4,5trimethoxyphenol 30 and 3-chloro-3-methylbut-1-yne with K 2 CO 3 , which gave the corresponding ether in addition to the related dieneone from para-attack. 35 It is of great interest that the dienone 33 is structurally similar to tarennane 34, a 45 natural product isolated from the whole plant of Tarenna attenuata that displays potent antioxidant activities against H 2 O 2 damage. 36 To prevent formation of the chroman and synthesise selectively the ortho-prenylated phenol 31a, we investigated 50 the protection of the phenol group in situ.…”

Synthesis of 3,4-Dihydro-4-Hydroxy-2,2-Dimethyl-2H-1-Benzopyran-5 8-Dione. A Potential Key Intermediate for the Preparation of Naphtho[2,3-b]Pyranoquinones

“…Acetate, yellow crystals, rn.p. 138.5-139.5 "C; lH-nmr 6: 1.51 (s, 3H, CH3), 1.56 (s, 3H, CH3), 2.09 (s, 3H, CH3), 2.16 (ddd, J = 15.0, 5.0 and 3.0 Hz, 2H, CH2), 6.10(dd,J=5.0and3.0Hz, lH,H-4),7.7-7.8(m,2HArH),8.1-8.2(m,2HArH).…”

Acremonoside, a phenolic glucoside from the sea fan-derived fungus Acremonium polychromum PSU-F125

“…As part of our research program on bioactive compounds from marine-derived fungi isolated from a sea fan of the genus Annella, we describe herein the isolation of a new phenolic glucoside (1) (Fig. 1) from the mycelial extract of Acremonium polychromum PSU-F125 together with two known compounds, F-11334 A 2 (Tanaka et al, 1999) and 2,2-dimethyl-2H-chromen-6-ol (Brown et al, 1990), from the broth extract. To the best of our knowledge, this is the first report on the chemical investigation of A. polychromum.…”