C-Nor-D-homo rearrangement

The C-nor-D-homo rearrangement has been effected by methods other than i2j sulphonate solvolysis, including the deamination of a i2jS-amine (7) [iii] and the decomposition of i2-toluene- sulphonylhydrazones (8) under basic conditions [io8,iog,ii2]. It is both convenient and instructive to consider these reactions together, especially since the com-... 

C-nor-D-homo rearrangement of a I4 hydroxy-i2) -tosyloxy steroid y. Shimizu and H. Mitsuhashi, Tetrahedron, 24 (1968) 4207. 

These results indicated that the Wagner-Meerwein-type rearrangement was followed by a stereospecific hydride transfer from C-18a to C-13a which led to an immonium ion, the latter finally being reduced to derivative (11) (Scheme 1). Inversion at position 12, as expected for a Wagner-Meerwein-type rearrangement, is in accordance with the generality of the c-nor-D-homo rearrangement. 

By the action of collidine, a successful c-nor-D-homo rearrangement of lip-mesyloxy-NJV -dicyanodihydroconimine (16a) in a non-reductive medium has been reported to give a mixture of two ethylenic main products. These have been shown to have tetrasubstituted double bonds and their possible structures are (17), (18), or (19). The presence of the derivatives (17) and (18) in the reaction... 

The C-nor-D-homosteroid rearrangement was discovered by Hirschmann and co-workers at the time that Wintersteiner and his collaborators established that the steroid alkaloids jervine and veratramine incorporate a 14 (1312) abeo-nng system. This was the predecessor of the family of simultaneous ring contraction-expansion reactions. Solvolysis of the 12j5-methanesulfonate (144a) gives mainly the kinetic reaction product, the C-nor-D-homo exocyclic olefin (145) along with some 13(17)-ene (146a). 

VII. 14(13 -> 12aH)y46eosteroids (C-Nor-D-Homo Steroids) / 400 By solvolysis of 12/ -methylsulfonyloxy steroids / 400 By fragmentation-rearrangement of 12-tosylhydrazones / 402... 

The oxidation of a 12-hydrazone (248) with lead tetra-acetate provided a novel route to rearranged steroids with the C-nor-D-homo structure (249), although another isomer was formed simultaneously. Dehydration of a C-12 cyanohydrin with thionyl chloride gave the 13a-cyano-c-nor-D-homo-compounds (250) and (251).209... 

Holarrhenine 12-mesylate is reduced by sodium borohydride in anhydrous alcohols with rearrangement to give a product with the c-nor-D-homo-struc-ture. The reaction is similar to that of a related conanine derivative, discussed... 

The C-nor-D-homo steroid alkaloids are formed from steroids by rearrangement of the ring system. The exact pathway is, however, still unknown. The alkaloids are poisonous to animals and act as feeding deterrents (E 5.5.3). They are effective insecticides. 

The 17,17-dimethyl-18-nor-13-ene (468), in sulphuric acid at 0 °C, afforded the rearranged and reduced product (469) in 60% yield.The D-homo-analogue reacted similarly. No detailed mechanism for the reduction (hydride donation) has been offered. 

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