4-Methoxyl benzoate

Tasaki M, Y Kamagata, K Nakamura, E Mikami (1992) Utilization of methoxylated benzoates and formation of intermediates by Desulfotomaculum thermobenzoicum in the presence or absence of sulfate. Arch Microbiol 157 209-212. 

The reaction goes faster in more polar solvents (a range of 106 in the rate constant) and parallels carbonium ion rearrangements in that respect. The effect of substituents in the para position of the benzoate group also suggests that the rate-determining step is the formation of an initial ion pair. The reaction is faster with the nitro than with the methoxyl substituent.819 820 The Hammett p value is 1.34. The activation parameters are not known for any but the unsubstituted member of the series however, and hence it is not known to what extent the relative rates depend upon the temperature. 

The effects of polar substituents on the alkaline hydrolysis of esters are well-established. Since the rate of the reaction is determined largely by the rate of addition of hydroxide ion to the carbonyl group of the ester, any substituent which withdraws electrons from the carbonyl group will increase the reactivity of the ester. The most accessible quantitative measure of the effect is the Hammett or Taft reaction constant, and a large number of measurements are available. Taft et al.2i0 found p = 2.53 for the base-catalyzed methanolysis of meta- and para-substituted (/)-menthyl benzoates, closely similar to the known value of p = 2.37 for the alkaline hydrolysis of substituted ethyl benzoates. Jones and Sloane s value239, obtained with five esters, of p = 2.41 for the methoxyl exchange reaction of substituted methyl benzoates in methanol, is almost identical. 

In a reaction that resembles the work of Gray and coworkers described above, Hughes and Speakman noted a 1—>4 migration of a methoxyl group in the reaction of the dimethyl acetal (22) with tetrabutylam-monium benzoate in iV-methylpyrrolidinone. The immediate product was the 4-0-methyl-ii-lyxose hemiacetal benzoate (24), which could be converted into the known 2-0-methyl-L-arabinitol (4-0-methyl-L-lyxitol)... 

The first example of methoxyl participation reported in carbohydrate chemistry was the migration454 of a methoxyl group from C-l to C-4 during an attempted benzoate displacement reaction with 2,3,5-tri-O-benzyl-4-O-p-tolylsulfonyl-D-ribose dimethyl acetal (185). Instead of the 4-O-benzoyl-L-lyxose derivative expected, the isomeric l-0-benzoyl-2,3,5-tri-0-benzyl-4-0-methyl-L-lyxose methyl hemi-acetal (187) was obtained, presumably by way of the cyclic, oxonium ion 186. Solvolysis of the related aldehydo sugar, namely, 2,3,5-tri-O-benzyl-4-O-p-tolylsulfonyl-D-ribose, readily gives 2,3,5-tri-O-benzyl-L-lyxofuranose, and the reaction probably involves participation by the free aldehyde group.455... 

Chasmaconitine (CCXCI) (C34H47NO9) exhibited signals in its NMR spectrum characteristic of four methoxyls, one acetoxy group, one benzoyloxy group, and A-ethyl (131). The IR spectrum confirmed the acetate and benzoate ester groups and in addition showed the presence... 

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