B-Homo steroids

A-Nor-B-homo steroids with different substitution patterns than those described above may be prepared by acid catalyzed cyclization of 3)3-hydroxy-5(10)-seco-cholest-tra/w-l(l0)-en-5-one acetate (134a) formed in 30-40% yield by mercuric oxide-iodine sensitized irradiation of cholestane-3j3,5a-diol... 

It has been shown that 7j8-fluoro-B-homo-steroids are much more stable than their 7jS-chloro-analogues. Aromatization of ring a of such 7)S-fluoro-B-homo-androstanes and -pregnanes, under various conditions, occurred without rearrangement of the carbon skeleton and without loss of fluorine. Whereas... 

A promising general method for preparing B-homo-19-norsteroids has been reported by Tadanier and Cole in a study of the horaallylic rearrangements of 19-substituted-A -steroids. The ready availability of 19-hydroxy-A -steroids cf. ehapter 12) makes this approach particularly attractive. 

A-nor-5a-cholestan-2-one, 419 B-norcholestenone, 430 19-Norcholestenone, 281 B-norcholesterol acetate, 429, 430 D-nor-11-dehydrocorticosterone acetate, 441 D-nordesoxycorticosterone acetate, 441 A-nor-B-homosteroids, 395 C-nor-D-homo steroids, 400 C-nor-1U- (a-hydroxyethyl) -pregnane-... 

Some 2-deoxy-analogues of rubrosterone have been reported.73 The synthesis commenced with a Bamford-Stevens reaction upon 3/3,17/3-diacetoxyandrost-5-en-7-one tosylhydrazone to yield the corresponding 5,7-diene. Successive chromic acid and selenium dioxide oxidation of this diene furnished the 2-deoxyrubrosterones (177 R1 = OAc, R2 = H, R3 = OH, X= 17/3-0Ac,H 5a-H) and (177 R = OAc, R2 = R3 = H, X = 17/3-OAc,H 5a-H) respectively. Alkaline hydrolysis of the latter derivative afforded an A-homo-B-nor-steroid (178). The rubrosterone (177 R1 = R2 = R3 = OH, X = O 5/3-H), which possesses antidiabetic activity, has been prepared by oxidative degradation of the cholestene (179), itself obtained from ecdy-sterone.74... 

Acid-catalysed rearrangements of highly alkylated ketones have been reported outside the steroid field [2go], but only one such steroid reaction seems to be known. It occurred when the 5j3-methyl-A nor-B-homo-6-ketone (i) was allowed to react with boron trifluoride, giving the normal 5 5-methyi-cholestan-4-one (3 [2gi], The initial ketone-BFg complex (i) may rearrange via the epoxide (2), although alternative bond-migration sequences can be formulated with the same end result. 

Tosylate rearrangement. Mazur devised an ingenious scheme for the synthesis of perhydroazulenes and first explored the stereochemistry by applying the reaction in the steroid series. Cholestane-5a,6a-diol 6-tosylate (1) is converted quantitatively into the A-homo-B-nor-5-ketosteroid (2) when refluxed with finely divided calcium carbonate-dimethylformumide for 6-8 hrs. or heated with potassium i-butoxide in f-butanol at 100°, C holeNtune-4( ..5 -diol 4-tosylate (3) gave A-nor-B-homo-.5-... 

CarbocycUc Steroids.— The Torgov synthesis continues to exhibit its great versatility and was recently employed in the first synthesis of B-homo-oestrone. Condensation of the vinyl alcohol (407) and 2-methy 1-cyclopentane-l,3-dione in the presence of l,4-diazabicyclo[2,2 ]octane and cyclisation with toluene-p-sulphonic acid gave the B-homo-oestrapentaene (409) in 33 % overall yield from 3-methoxybenzosuberone. A three-stage reduction by sodium borohydride, catalytic hydrogenation, and lithium-ammonia afforded 3-methoxy-B-homo-... 

Brassinolide (BR), (2a,3a,22a,23a-tetrahydroxy-24a-methyl-B-homo-7-oxa-5a-cholestan-6-one), a biologically active steroidal lactone first isolated from rape Brassica napus L.), pollen, stimulates growth of green plant tissues. Although the mechanism responsible for observed BR effects remains to be determined, the action of BR on growth is oligodynamic, and rapid. 

Electrophilic Addition.—The hydroxylation of alkenes, including several steroids, with osmium tetroxide has been reviewed. Addition of HOBr to the 19-functionalized-5a-cholest-6-enes (13) gave mixtures of the corresponding bromohydrins (14) and the 6,19-epoxides (15) whereas the analogous B-homo-compounds (16) gave only the 6,19-epoxides (17). Similar effects were noted for the related HBr- and HC104-catalysed opening of the 6a,7a-epoxides and it was observed that the predominant attack by the 19-0 atom [5(0)" attack] in the B-homo-series lay in the possibility of its linear approach with the C-6—Br or C-6—O bond. The reactions of chromyl chloride and chromyl fluoride with steroidal alkenes and dienes have been reported " and it was observed that the... 

The reactions of bromohydrins in the cholestane series with Ag20 have been shown to depend markedly on the conformation of the bromine. Thus, for example, the 6a-bromo-7 -hydroxy-compounds (107) and (108), which have the equatorial bromine, gave the B-nor-aldehyde (110) whereas the 6/8-bromo-7/S-hydroxy-compound (109) gave the 7-oxo-compound (111) via a hydride shift. Hydrolysis of the dipotassium 5)3-pregnane-3a,20a-diyl sulphate in 3N-HC1 gave the D-homo-steroids (112) and (113) in addition to the expected... 

A normal or B-homo cholestane, ergostane, or sitostane steroidal skeleton... 

Hirschmann, F. B., and H. Hirschmann Inversions of Both Adjacent Centers in the Formolysis of a 2,2,6-Trialkylcyclohexyl Tosylate. Formation of a 13a-D-Homo Steroid. J. Organ. Chem. (USA) 38, 1270 (1973). 

In the course of synthetic efforts aimed at obtaining 6j5-fluoro steroids, Kirk and Petrow treated a 3)5-acetoxy-6-raethyl-5a,6a-epoxide with boron trifluoride etherate and unexpectedly obtained a fluorine-free acetoxy ketone." Later transformations established that the product was the A-homo-B-norsteroid (104). 

Oxime 26 was prepared from 5,ll-dihydro-dibenzo[a,d]cyclohepten-10-one. The Hoch-Campbell reaction of 26 with 3-dimethylaminopropylmagnesium bromide produced aziridine 27 in 46% yield after acidic workup. Extension of the Hoch-Campbell reaction to steroids has also been reported. Thus, treatment of 3(3-hydroxy-5-pregnen-20-one oxime (28) with methylmagnesium iodide furnished a mixture of diastereomers, 20ot/20P,21-imino-20-methyl-5-pregnen-3P-ol (29) in a 50% combined yield and a 3 1 ratio. On the other hand, homo-adamantan-4-one oxime (30) was transformed to homo-adamantano[4,5-b]-2 -ethylaziridine (31) in 76% yield upon the action of... 

In the steroid field a rare instance of epoxide formation by diazo-tiz tion of a 0-amino alcohol is the conversion of certain B-hortm-ftteroid derivatives into the corresponding 17<, 17aa-epoxy D-homo... 

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