Carboxylic acids, addition compounds with detection

Several studies have dealt with the problem of discriminating between mastic and dammar, and three marker compounds of mastic have been identified moronic, masticadienonic and acetyl masticadienolic acids [42], The chemical structure of (iso)masticadienonic acid and 3-0-acetyl-3-epi(iso)masticadienonic acid is characterized by a side chain, as for dammarane molecules, but with a carboxylic acid end group (Table 12.1). Under pyrolysis conditions this side chain is susceptible to cleavage as demonstrated by the presence, among the pyrolysis products of mastic, of 2-methyl-pent-2,4-dienoic acid, that perfectly matches with the chemical structure of the side chain end. In addition 3-(9-acetyl-3-epi-(iso)masticadienolic acid also loses the acetyl group and, in contrast to masticadienonic acid, is not detected at all. 

GC analysis of underivatized polar fractions did not reveal any volatile sulfur compounds. However, once these fractions were methylated with diazomethane, a number of sulfur compounds were detected. (Presumably, the diazomethane methylated either carboxylic acid, phenolic, thiophenolic, sulfonic acid or even alcohol or thiol groups and thereby increased their parent molecules volatility). These additional sulfur compounds are currently under investigation in our laboratories and the results of these studies will be reported later. 

Lactones are normally stable compounds, which have found ample application as synthetic intermediates, and, quite recently, have been detected as the central structural unit in physiologically active natural products like obaflorin (123) and lipstatin (124). Characteristic applications of 3-lactones in synthesis are the stereospecific CO2 elimination to form di- and tri-substituted alkenes (e.g. from 125 equation 40) or Grignard addition to the carbonyl group e.g. equation 41). Particularly useful is the formation of 3-lactone enolates (126), which react with a variety of electrophiles (EX) wiA high stereocontrol (equation 42). Organocuprates may be used in chain elongations to form 3-branched carboxylic acids (equation 43). ... 

It might be expected that in the presence of TMEDA or other tertiary diamines anomalous reaction products might be obtained with organolithium compounds such as benzyllithium. A number of reports in the literature disclose instances of the expected reaction products from reactions such as carbonation to the carboxylic acid and addition to benzophenone (I, 3, 4, 12). The phenyllithium-TMEDA (1 1) complex in benzene was allowed to react with benzophenone to give a 95% yield of triphenylcarbinol and with cyclohexanone to yield 59% of the 1-phenylcyclohexanol. The reaction with excess trimethylsilyl chloride is apparently quantitative. The main consideration in using these complexes is to use low temperatures for reaction and aqueous washes of ammonium chloride solution in the work-up to remove all of the tertiary diamine (the odor can be detected in low concentrations.)... 

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