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Vitamin D derivatives containing two side chains emanating at C-20 are known as gemini. We have recently synthesized two gemini which are related to calcitriol and 19-norcalcitriol containing two identical side chains. The metabolism of these species involves 24(R)-hydroxylation on one of the side chains. To determine the outcome of this diastereospecific transformation, we synthesized both C-20 epimeric pairs containing the 24(R)-hydroxy group in the gemini and 19-norgemini series. On the basis of the availability of these reference compounds, it was shown that the metabolic hydroxylation occurred at the pro-R side chain in both gemini compounds. In comparison to the parent compounds, the 24-hydroxygemini required higher doses to increase blood calcium levels in mice and to suppress INF-γ release in MLR.

The chemical vocabulary can describe, in a single term, a racemate or a specific enantiomer or a compound that is enantiopure, but whose absolute configuration is unknown. Regardless of these differentiations, the corresponding conventional graphic representations display but one specific enantiomer. Because of this inflexibility, verbal annotations to stereostructures in chemical publications and databases are unavoidable. In the expanding era of chirotechnology, the limited descriptive power of stereostructures in two-dimensional space is of serious concern. To provide a solution to this problem, targeted redeployment of established stereobonds serve as stereodescriptors that differentiate between enantiopure and racemic compounds and those that are enantiopure but whose chirality sense is unknown. Graphic displays then share the explicitness and accuracy of the chemical vocabulary. Fischer projections, recently expanded to accommodate alkenes and axially stereogenic compounds, can display favorably comparative configurational aspects of molecules with a multiplicity of stereogenic units.

A gentamicin C-complex preparation was separated preparatively into five components by Craig distribution. Gentamicins C1, C2, and C1a, were the major components, whereas components C2aand C2brepresented only 4% of the total C-complex mixture. Paper chromatographic analysis showed that the gentamicin C2bseparated by Craig distribution was identical with a gentamicin isolated from Micromonospora purpureavar. JI-33 fermentation broth and identified as 6′-N-methylgentamicin C1a. Similarly, component C2a, was identical with a previously separated gentamicin component tentatively identified as the 6′-C epimer of gentamicin C2.