6-Methoxy-2,2-dimethylchromene

Boyd, D.R., Sharma, N.D., Boyle, R., Evans, T.A., Malone, J.E., McCombe, K.M., Dalton, H. and Chima, J., Chemical and enz3mie-catalysed syntheses of enantiopure epoxide and diol derivatives of chromene, 2,2-dimethylchromene, and 7-methoxy-2,2-dimethylchromene (pre-cocene-1). J. Chem. Soc. Perkin Trans. 1,1996, 1757. 

Chromenes (Phe a-pyran) include encecalin (a phototoxic antimicrobial from various Asteraceae) and the phloroglucinol derivative mallotochromene (cytotoxic and an HIV-1 reverse transcriptase inhibitor). Precocene 1 (7-methoxy-2,2-dimethylchromene) and pre-cocene 2 (6,7-dimethoxy-2,2-dimethylchromene) produced by Ageratum species (Asteraceae) inhibit the production of insect juvenile hormone (JH) as a result of suicidal conversion of these pro-toxins to cytotoxic derivatives by the JH-producing insect cells. 

Also obtained by oxidation of encecalol [6-(l-hydroxyethyl)-7-methoxy-2, 2-dimethylchromene] (encecalol) with manganese oxide in petroleum ether suspension for 2 h at r.t. (84%) [4302],... 

Condensation of S-amino 7-methoxy-2,2-dimethylchromene (343) with dimethylacetylenedicarboxylate (351) gave 362, which was converted to 363 by reaction with allyl bromide in alkaline medium. Cope rearrangement of 363 into 364, ensued by heating in ether, permitted creation of ring B of the target compound. Reduction of the carbomethoxy group of 364 by lithium aluminum... 

Ru(CO)(den-por) (den-por=dendritic porphyrins). These are made by condensation of Ru(CO)L (L=5,10,15,20-tetrato(4 -hydroxyphenyl)porphyrin or 5,10,15,20-tetrakis(3, 5 -dihydroxy-phenyl)porphyrin), themselves made from RUjlCO) and (L), with poly-(benzylether) dendrons H, C NMR, electronic and IR spectra of the products were measured. Epoxidation of cyclic alkenes, cis- and tranx-sfilbene, styrene and its 3-methyl, methoxy, chloro and bromo derivatives, dimethylchromene and of cholesteryl esters in high yields and turnovers was effected by RulCOKden-porl/lCl pyNOl/CHjClj [871]. 

Hydroxyphenyl)-5-methoxy-6-(3,3-dimethylallyl)-2",2"-dimethylchromene-(5",6" 8,7)-3-(propyl-2-one)-47T-l-benzo-2,3-dihydropyran-2,4-dione. 

Precocenes I and II are natural products with a simple chromene structure (7-methoxy- and 6,7-dimethoxy-2,2-dimethylchromene) which were isolated from plant sources and exhibited powerful antijuvenile hormone activities in several types of insects (1). 

Preliminary results of antijuvenile hormone bioassays for precocious metamorphosis in immature stages of Oncopeltus fasciatus revealed that some of the non-linear derivatives (VI) showed higher activities and lower toxicities that those exhibited by natural precocenes or 7-ethoxy-6-methoxy-2,2-dimethylchromene, one of the most active synthetic analogs known. In addition, some of these compounds were unexpectedly inactive in the sterilization bioassay with adults of the same species (8). Further investigation of antijuvenile hormone activities of selected compounds of this series in other insects is now in progress. 

Methoxy-2,2-dimethylchromene (23.5) and benzofuran 23.2 have also been synthesized by alkylation of 4-methoxyphenol to 2-(3-methyl-2-butenyl)-4-methoxyphenol (22.1), followed by acid catalysed cyclization of the corresponding epoxyde 22.3 to 23.3 and 23.6. Dehydration of 23.6 with p-TsOH gave 23.5, while NBS dehydrogenation of 23.3 afforded 23.2 (102). 

Grignard reactions on coumarins are a source of various compounds for example, coumarin and methylmagnesium iodide yields 2,2-dimethylchromene and nine other products, which have been identified by g.l.c.-m.s. A similar reaction on 8-methoxy-6-methylcoumarin gave 8-methoxy-2,2,6-trimethyl-chromene, which was oxidized by DDQ to the 6-carboxaldehyde. The reaction of 3,4-diaryl-coumarins with methylmagnesium iodide gives various products, depending on the substituents present, the polarizability of the carbonyl group, and the reaction conditions. 

Prenyl substitution is a conventional derivatization style in stilbenes, exemplified by artoindonesianin N 29 immArtocarpus gomezianus [17]. The prenyl groups in stilbenes cyclize to form new derivatives. 4-Hydroxy-5 -methoxy-6",6"-dimethylpyran[2",3" 3, 4 ]stilbene 30, 3,5 -dimethoxy-4-hydroxy-6",6"-dimethylpyran[2",3" 3, 4 ]stilbene 31, and 3,4,5-trimethoxy-6",6"-dimethylpyran [2",3" 3, 4 ]stilbene 32, with dimethylchromene ring in their structures, have been obtained from Lonchocarpus utilis (Leguminosae) [18]. Furthermore, schweinfurthins A-C 33-35 from the leaves of Macaranga schweinfurthii (Euphorbiaceae) are typical samples of the prenylated stilbenes [19]. 

Tandem metallation synthesis of acridones was also successfully applied by Watanabe to the synthesis of acronycine (2) (314). Thus, the lithium sdt of methyl A -methylanthranilate (250) easily reacted with the benzyne 348 generated from 6-bromo-9-methoxy-2,2-dimethylchromene (349) (357) to afford directly acronycine (2) in 41% yield. 

Hydroxy-5-methoxy-2-hydroxymethyl-2,8-dimethylchromene (Pterochromene L4) Pteris longipinna Hayata C13H16O4. oil + 11.0 91... 

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