Transformed steroids. 133. Synthesis of 20-deoxysteroids with a tetrahydropyran ring E

The synthesis of 20-deoxy compounds — the precursors of the steroid pyranols and pyranones synthesized by the authors previously — has been effected from a steroid 20-ketotetrahydropyran by the hydrogenolysis of the corresponding ethylene dithioketal with Raney nickel. The¹H and¹³C NMR spectra have been studied in detail. Transformations of rings A and B via the epoxide or the 3,5-cyclosteroid have led to 3-acetoxy-16,23-epoxy-5H-21,24-dinorchol-5-en-6-one and 3-acetoxy-5-hydroxy-16,23-epoxy-21,24-dinorchol-5-en-6-one.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 732–735, November–December, 1983.     

Transformed steroids 117. Synthesis of 5α-hydroxy-6-oxosteroids with a δ-lactone ring E

The paper is devoted to the synthesis of steroidal 5-hydroxy-6-oxolactones from ethyl esters of 5,6-dienic acids. By epoxidating the latter it has been shown that, in addition to the usual formation of 5,6-oxides, opening of the 16, 17-oxide ring initially formed takes place and this is accompanied by intramolecular cyclization to a 17,20-dihydroxy--lactone. The trans-opening of the 5,6-epoxide in the epoxy--lactone and subsequent oxidation with N-bromosuccinimide has led to a new representative of steroidal -lactones — the 23,16--lactone of the 3-acetate of 3, 5, 16, 17, 20-pentahydroxy-6-oxo-24-norcholan-23-oic acid.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 208–213, March–April, 1980.     

Development of a stereoselective co-mediated dihydropyran ring contraction

A highly stereoselective approach for the synthesis of trans-1,2-disubstituted cyclobutanes through an Al-promoted cobalt-mediated O-->C ring contraction of dihydropyrans is described. [reaction: see text].     

Transformed steroids. 123. Synthesis of 5α(H)- and 5α(OH)-6-ketosteroids with an additional 17α,20ξ-dihydroxytetrahydropyran ring E

The paper is devoted to the synthesis of 3,17α,20-trihydroxy-16β,23-epoxy-21,24-dinor-5αH-cholan-6-one and 3,5α,17α,20-tetrahydroxy-16β,23-epoxy-21,24-dinorcholan-6-one and derivatives of them. It has been shown that the reduction of 3,17α-dihydroxy-16β,23-epoxy-21,24-dinorchol-5-en-20-one with sodium tetrahydroborate and with diborane takes place stereospecifically with different spatial directivities: in the products of diborane reduction, ring E exists in the boat form, as has been shown by¹H and¹³C NMR methods. The trans linkage of rings A/B in the modified steroids has been confirmed by their circular dichroism spectra.     

Transformed steroids. 161. Reactivity of 17-spirooxetane-20-ketosteroids towards opening of the four-membered ring

Conclusions Replacement of the 20-oxo group in 17,21-epoxypregn-5-en-3-ol-20-one by the hydrazono-group affects the cleavage of the oxetane ring by thiocyanic acid, reaction occurring preferentially by introduction of^–NCS at C¹⁷ with consequent expansion of the four-membered ring to a six-membered ring with the formation of the [17; 21]-1,3-tetrahydrooxazine-2-thione.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1393–1396, June, 1987.     

The reactions of dihydropyran and 2-methyldihydropyran with some Schiff bases

Summary Schiff bases such as benzylideneaniline, benzylidene-p-anisidine, benzylidene--naphthylamine, and thienylideneaniline react in the presence of BF₃ with dihydropyran and 2-methyl-4,5-dihydrofuran by diene addition to form 1,2,3,4-tetrahydroquinoline derivatives as adducts.     

Transformed steroids. 181. Synthesis of 16α,17α-cyclohexano-19-norprogesterone

Oxidative functionalization of the 19-angular methyl group of pregna-D₆-pentarane with its subsequent removal gave 16,17-cyclohexano-19-norprogesterone.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1636–1638, July, 1990.     

Synthesis and ring contraction reactions of polyazamacrolides

The synthesis of three analogues of the single most abundant component of a ladybird beetle (Epilachna borealis) defensive secretion, the trimeric 42-membered polyazamacrolide PAML 681, is described. Construction of the nonnatural macrocyclic trimers began with the preparation of the corresponding monomeric segments, followed by their oligomerization and a final macrolactonization step of the activated linear trimeric hydroxy acid. The relative rates of the O-to-N acyl migrations that are characteristic of PAML 681 itself, as well as of the synthetic analogues, were investigated. These studies showed that changes in the substitution pattern adjacent to the nucleophilic nitrogen atom, along with changes in the size of the oxaazacyclic intermediates, have substantial effects on the polyazamacrolide rearrangement rates.     

Transformed steroids. 113. Cyclobuteno [16α,17α]pregnanes in cycloaddition and oxidation reactions

Conclusions The strained double bond in cyclobuteno[16,17]pregnanes is reactive toward certain dienes and oxidizing agents; here its reactivity toward dienes is increased by high pressure.See [1] for Communication 112.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1902–1904, August, 1980.     

Transformed steroids 129. Synthesis of 6α-methyl-16α,17α-cyclobutanoprogesterone

Conclusions A synthesis of 6-methyl-16.17-cyclobutanopregn-4-ene-3,20-dione was carried out by opening the 5,6-oxide ring with a Grignard reagent, with preliminary protection of the 20-keto group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2151–2154, September, 1982.     

Transformed steroids 126. Synthesis and stereochemistry of isomeric androsta-D'-pentaranes (15,16-cyclohex-3′-enoandrostanes)

Conclusions Condensation of androsta-5,16-diene-17-one with 1,3-dienes at high pressure proceeds nonselectively, and leads to two diastereomeric cycloadducts, while in the presence of anhydrous AlCl₃ 15,16-cycloadduct is formed stereospecifically.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2147–2151, September, 1982.     

Transformed steroids. 114. Direction of opening oxide ring of 16,17α-epoxy-17β-phenylandrost-4-en-3-one

Conclusions Starting with androst-5-en-3-ol-17-one, we synthesized 16,17-epoxy-17-phenylandrost-4-en-3-one. Cleavage of 17-C-O bond, adjacent to the phenyl ring, occurs during its nucleophilic opening, accompanied by 1,2-migration of the angular 18-CH₃ group.See [1] for Communication 113.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1889–1893, August, 1980.