SYNTHESIS OF 17-(2-METHOXY-3-OXAZOLIN-4-YL), 17-(3-OXAZOLIN-4-YL), AND 17-(2-OXAZOLIN-4-YLIDENE)-SUBSTITUTED STEROIDS AND THEIR USE AS PRECURSORS OF CORTICOSTEROIDS

17-(Isocyanotosylmethylene)steroids 4 are useful intermediates in the conversion of 17-oxosteroids into 17-(hydroxyacetyl)steroids. The 21-CH2OH group is effectively introduced by a base-mediated reaction of compounds 4 with formaldehyde and MeOH to give 17-(2-methoxy-3-oxazolin-4-yl) derivatives 12, which by acid hydrolysis give 17-(hydroxyacetyl)steroids 10 and 16 in high yields. Partial hydrolysis of the same oxazoline derivatives 12 provides the 17-(hydroxyacetyl) cortico side chain of 13 equipped with a formyl-protected hydroxy group. 3-Oxazolinyl and 2-oxazolinylidene steroid derivatives 19, 20, and 21, without a 2-methoxy substituent, are discussed as alternatives of 12.