Of vitamin D derivatives

Studies of the effects of oral contraceptives on serum concentrations of vitamin D derivatives have given variable results. 

Systematic nomenclature of vitamin D derivatives utilizes the obvious relationship to steroids, and the term seco (ring opened) is incorporated into the root name (compare secologanin as a... 

Since the completion of the first total synthesis of calciol (1) by H. H. Inhoffen, H. Burkhardt and G. Quinkert in 1959 [3], several research groups have focussed their activities on the synthesis of vitamin D derivatives [4]. In the course of these investigations, two particularly powerful strategies have been identified, which still today [5J form the basis of many syntheses of la-hydro-xylated vitamin D derivatives (Schemel). 

A synthesis of the Inhoffen-Lythgoe diol (46.7, Scheme 2.46), a useful intermediate in the synthesis of Vitamin D derivatives, demonstrates the use of a chiral acetal in an asymmetric tandem cyclisation reaction.102 Once again, Lewis acid co-ordination to the less hindered oxygen of the acetal 46.1 initiated a Prins-like cyclisation that terminated by attack of the propargylsilane on an incipient tertiary carbocation. After removal of the chiral auxiliary, the allene function in the alcohol 46.4 was transformed into the side chain of 46.7 with the creation of two new stereogenic centres. 

The compound (18) derived from 15 [31] was the good synthetic intennediate for the preparation of the 2p-hydroxylated active fonns of vitamin D derivative such as ED-71 [32]. Epoxidation of 50 derived from the ozonolysis of 18 followed... 

Scheme (5). Synthesis of active forms of vitamin D derivatives (via cyclovitamin D derivatives)... 

The UV absorption of vitamin D In solution (e 19,500) points to the predominance of the cZt form, which Is Indicated also by the FMR data. Furthermore, this conformer Is the one found In the crystalline state of vitamin D derivatives as demonstrated by the X-ray analyses of Hodgkin Crowfoot, Webster, and Dunltz (71) (calciferol 4-lodo-3-nltrobenzoate) and Knobler al. (72a)... 

Syntheses of Vitamin D Derivatives. The starting materials in the synthesis of vitamin D by Inhoffen s method are bicyclic in-dans containing oxygen functions in positions 8 and 17 according to the steroid nomenclature. The methods of obtaining these products are illustrated in Scheme 89. 

Several chemical reactions could be carried out on a microscale for the preparation of vitamin D derivatives for GLC. 

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