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The development of a 21 -alkylation reaction which proceeds via the lithium 20(21)-enolate is described and its scope demonstrated by the preparation of a variety of 21 -alkylpregnane derivatives. Application of this process to 1 l~-acetoxy-l6a,l7a-dimethyl-5ct-pregnane-3,2O-dione (28a) and its 5P-analogue (28b) led to the corresponding 16a,l7a,21 -trimethyl derivatives. Several routes from these saturated trimethylpregnane-3,2O-diones to 1 1 P-hydroxy-l6a,17a,21 -trimethylpregna-l,4-diene-3,20-dione (Org 621 6) were explored. The best method gave Org 621 6 in 75% yield. (61 000); vmSx. 1 707 cm-l (11-ketone) (Found, M+, 592.4262. C12Hb802 requires M , 592.4280) with zinc in acetic acid.

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