Stereoselective Synthesis and Determination of the C-16 Configuration of 16-Halomethyl/16-Hydroxymethyl Steroids

Pál Sohár; Attila Fürjes; János Wölfling; Gyula Schneider

doi:10.1055/s-1992-26358

Synthesis 1992; 1992(12): 1280-1283
DOI: 10.1055/s-1992-26358

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Stereoselective Synthesis and Determination of the C-16 Configuration of 16-Halomethyl/16-Hydroxymethyl Steroids

Pál Sohár^* , Attila Fürjes, János Wölfling, Gyula Schneider

^*Spectroscopic Laboratory, Department of General and Inorganic Chemistry, Eötvös Lóránt University, P.O. Box 32, H-1518 Budapest-112, Hungary

Abstract

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A considerable stereoselectivity was found during the hydroxy → halogen exchange reaction of 16,16-bis(hydroxymethyl)-17-oxo- and -17-β-hydroxy-3-methoxyestra-1,3,5(10)-trienes depending on the starting materials and on the conditions of the reaction. The 17-oxo steroid 1 is transformed by acetic acid/hydrogen bromide solely into 16β-acetoxymethyl-16α-bromomethyl-3-methoxyestra-1,3,5(10)-trien-17-one (3a). In contrast, the 17β-hydroxy steroid 4 yields a mixture of the two 16-epimers 7a and 8a. The formation of these brominated steroids can be interpreted in terms of front-side neighboring group participation. The hydroxy → halogen exchange of 16,16-bis(hydroxymethyl)-17β-hydroxy compound 4 with carbon tetrachloride or carbon tetrabromide in the presence of triphenylphosphine proceeds stereoselectively, and only the 16β-halomethyl epimers 8a and 8b are formed. Constitutions of the new steroids were proved by IR, ¹H and ¹³C NMR spectra. The C-16 configuration of the epimeric pairs was determined by NOE measurements.

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