G.l.c. examination of bile alcohols prepared from the sucker Catostomus commersoni Lacépède (family Catostomidae) showed that although 5alpha-cyprinol (5alpha-cholestane-3alpha,7alpha,12alpha,26,27-pentol) was a minor constituent, the principal bile alcohol was an undescribed substance, probably present in the bile as the C-26 sulphate ester, whose i.r., n.m.r. and mass spectra agreed with the structure 5alpha-cholestane-3alpha,7alpha,12alpha,24,26-pentol. 2. M(D) studies suggest that this 5alpha-chimaerol is the 24(+), 25S enantiomer and that 5beta-chimaerol (chimaerol) from Chimaera monstrosa bile also has the 24(+), 25S configuration. These findings imply that bile alcohol biosynthesis in suckers and chimaeras includes stereospecific oxidation of cholesterol at C-26. 3. C. commersoni bile acids (present in minor amounts) probably consist largely of 3alpha,7alpha,12alpha-trihydroxy-5alpha-cholan-24-oic acid (allocholic acid). 4. 5alpha-Chimaerol sulphate and 5alpha-cyprinol sulphate are probably biochemically equivalent as bile salts, and can be considered as arising by parallel evolution.
