Methyl 2-methoxy-3,6-dimethyl-4-hydroxybenzoate

Methyl iso-rhizonate. Methyl 2-methoxy-3,6-dimethyl-4-hydroxybenzoate (Iso-rhizon-sauremethylester, 2-Methoxy-3,6-dimethyl-4-hydroxybenzoesauremethylester)... 

The IR (1690 cm ) and UV (257 nm) spectra, and the formation of a 2,4-dinitrophenylhydrazone supported the presence of an a,p-unsaturated carbonyl group in tomentellin (581). Hydrogenation of (581) which gave methyl 3-methoxy-4-hydroxybenzoate and tetrahydroderivative, and analysis of the H-NMR and mass spectra [m/z 181 +H (65%) and 151 (100%)] led to the conclusion that tomentellin was 3,7-dimethyl-5-keto-2,6-octadienyl 3,4-dimethoxybenzoate (581). The position of the carbonyl group was further confirmed by the bathochromic shift of the UV absorption band to 257 nm after addition of aq. NaOH. The geometry of the enone system was presumed to be s-cis from the observation that the IR absorption band of the double bond was more intense than that of a carbonyl group. 

Hydrolysis of the fourth isoprenyl benzoate (584) gave vanillic acid. Methylation of (584) afforded tomentellin (581). Thus, the structure of demethoxytomentellin was established to be 3,7-dimethyl-5-keto-2,6-octa-dienyl 3-methoxy-4-hydroxybenzoate (584). 

Hydroxybenzo[6]thiophene has been isolated from coal tar.42 It may be prepared from 6-aminobenzo[fr]thiophene by standard procedures.241 6-Methoxybenzo[h]thiophene may be prepared by decarboxylation of the corresponding 2-carboxylic acid,341 and 6-ethoxybenzo[6]thiophene is obtained by reduction of 6-(ethoxy)-thioindoxyl (Section VI, 1,2). 6-Methoxy-5-methylbenzo[6]thiophene is obtained by cyclization of (3-methoxy-4-methylphenylthio)-acetaldehyde dimethyl acetal (Section IV,B).617 The product previously described542 as 6-hydroxy-3-phenylbenzo[6]thiophene has now been shown to be the 2-phenyl isomer.307 6-Methoxy-818 and 6-methoxy-5-methyl-benzo[6]thiophene617 are demethylated by pyridine hydrochloride. 

Of the four monohydroxybenzo[c]cinnolines the 2- and the 4-isomers are potentially tautomeric with the corresponding quinonimines, e.g., 90 91. While the ultraviolet spectrum of 2-hydroxybenzo[c]cinnoIine shows close correspondence to that of the 2-methoxy compound in neutral solution, spectra of the conjugate acid and conjugate base both indicate appreciable charge-resonance between the 2- and 6-positions, and methylation of 90 with dimethyl sulfate or diazomethane gives rise to mixtures of 2-methoxy-benzo[c]cinnoline and the quinonimine 92. ... 

From 2-methoxy-3,6-dimethyl-4-benzyloxy-5-chlorobenzoic acid and methyl 2-methoxy-3,5,6-trimethyl-4-hydroxybenzoate with TFAA and subsequent debenzylation... 

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