作者:Daan van Leusen、Erik van Echten、Albert M. van Leusen
DOI:10.1002/recl.19921111102
日期:——
The synthesis is described of a series of eighteen 16-dehydro-20-isocyano-20-sulfonylpregnanes (5 and 8–14) by C-20 alkylation of 17-[isocyano(sulfonyl)methylene]androstanes 1–3. The geminal isocyano and sulfonyl groups at C-20 (compounds 5, 8–14) are removed by acid hydrolysis to provide a new entry into 20-oxosteroids (6, 15–19). The C-20 alkylation also includes halomethylation and alkoxymethylation
A novel process for the preparation of 20-keto-.DELTA..sup.16 -steroids comprising reacting a 17-(isocyanosulfonylmethylene)-steroid with an alkylating agent QR.sub.4 wherein R.sub.4 is an organic group and Q is a group or atom readily displaced with a nucleophile to form a 20-isocyano-20-sulfonyl-.DELTA..sup.16 -steroid followed by hydrolysis which are intermediates for the preparation of corticosteroids and the novel intermediates formed therein.
Reactions of corticoid precursor steroids with a DELTA16-double bond and iodine, trimethylsilyl, tributylstannyl or trifluoromethanesulfonyloxy groups in 17-position were studied with the aim of introducing an acyl substituent in 17-position. Starting with the 17-trimethylsilyl compounds, using acyl chlorides and AlCl3 as a catalyst, a mixture of chlorinated compounds were obtained, among others. Better results gave palladium-catalyzed reactions, such as the cross-coupling of 17-tributylstannyl compounds with acyl chlorides or the substitution of the 17-iodides or the 17-triflates by vinyl ethers. In the reaction of the 17-iodides, different protecting groups are tolerated; thus this method is of general use. No DELTA16-17-triflates were obtained by the reaction of androsta-4-ene-3,17-dione or androsta-1,4-diene-3,17-dione with trifluoromethanesulfonyl anhydride. This is a limitation of the triflate method, which in the other cases gives the best yields (> 80 %).
New process for the preparation of 20-keto-delta16-steroids and new intermediate compounds formed in this process