Methoxylation of methyl 3alpha,7alpha-dihydroxychol-4-en-24-oate and its 3beta-epimer. A contribution to chenodeoxycholic acid biogenesis.

By the conventional methods of gas liquid chromatography (GLC) as well as mass spectrometry, 3beta,7alpha-dihydroxychol-5-en-24-oic acid (delta5-acid), a key intermediate of chenodeoxycholic acid biogenesis and its metabolic by-product, 3alpha,7alpha-dihydroxychol-4-en-24-oic acid (delta4-acid) have not yet been identified as such probably due to thermal decomposition. However, taking advantage of the observation that they are readily methoxylated in methanol containing a trace of acids, their individual methoxy-compounds were easily prepared and proved to be useful for their identification, even though they are present in minimal amounts as was the case with the human or hen bile. The present paper reported physical as well as spectral properties of the methoxy-compounds derived from methyl 3alpha,7alpha-dihydroxychol-4-en-24-oate, compared with those of its 3beta-epimer.