Olovotetraacetatna oksidacija Dils-Adlerovog adukta 7-dehidro-holesteril-acetata sa anhidridom maleinske kiseline

The Diels-Alder adduct (3), obtained by cycloaddition of 7-dehydrocholesteryl acetate (1) and maleic anhydride (2), was heated at ca. 90 oC with a large excess of lead tetraacetate in pyridine solution for 5 h. Under these conditions, compound 3 underwent lactonization with the participation of the olefinic D6 -double bond to give two isomeric monolactone derivatives, 9 and 10 (in a total yield of ca. 6%), and the bislactone product 11 (in 11.5% yield). The starting material was recovered in 36% yield.Dils-Alderov adukt 3, dobiven cikloadicijom 7-dehidroholesteril-acetata 1 i anhidrida maleinske kiseline 2, oksidovan je velikim viškom olovotetraacetata u piridinskom rastvoru na oko 90 ºC u toku 5h. Pod navedenim uslovima izvršena je oksidativna laktonizacija jedinjenja 3 sa participacijom olefinske D6 -dvogube veze pri čemu su dobivena dva izomerna monolaktonska derivata 9 i 10 (u ukupnm prinosu od oko 6%) i bislaktonski proizvod 11 (u prinosu od oko 11,5%); pri tome je nepromenjen polazni adukt izolovan u prinosu od »36%.The authors are grateful to the Serbian Academy of Sciences and Arts, and the Ministry of Sciences and Technology of Serbia for financial support

Hidridna redukcija B-norholestan 5α,6α-epoksida

B-Norcholestane epoxide 2 is reduced with lithium aluminium hydride to give either the 3β,6α-diol 3 or the corresponding 3β,5α-diol 4, depending on the quality of the reducing reagent employed. Aplausible mechanistic explanation of the obtained results is suggested.Redukcijom B-norholestan-epoksida 2 pomoću litijum-aluminijum-hidrida dobijeni su odgovarajući 3β,6α-diol 3 ili 3β,5α-diol 4, u zavisnosti od kvaliteta upotrebljenog redukcionog reagensa. Predloženo je verovatno mehanističko tumačenje dobijenih rezultata

Oksidativne fragmentacije 5-hidroksi-1-okso-5α-holestan-3β-il-acetata

5-hydroxy-1-oxo-5α-cholestan-3β-yl acetate (11) was prepared in 5 steps starting from (E)-3β-acetoxy-5,10-seco-1(10)-cholesten-5-one (6). Treatment of the 1-oxo-5-hydroxy derivative 11 with lead tetraacetate (LTA) (under thermal or hypoiodite conditions) or with mercuric oxide/iodine (HgO/I2) reagent resulted in the oxidative β-fragmentation of the C(5)–C(10) bond affording 1,5-dioxo-5,10-secocholest-10(19)-en-3β-yl acetate (12), in different yields, depending on the reagent. Also the stereochemistry of the 1β,6β-cyclization product 13, formed by transannular cyclization of the 1,5-diketone 12 on silica gel, is discussed in this work.Sintetizovan je 5-hidroksi-1-okso-5α-holestan-3β-il-acetata (11) u 5 faza polazeći od (E)- 3β-acetoksi-5,10-seko-1(10)-holesten-5-ona (6). Dejstvom olovo-tetraacetata (LTA) (pod termičkim ili hipojoditnim uslovima), ili merkuri-oksid/jodnog reagensa (HgO/I2) na 1-okso-5-hidroksi derivat 11, vrši se oksidativna β-fragmentacija njegove C(5)–C(10) veze, pri čemu se dobija 1,5-diokso-5,10-sekoholest-10(19)-en-3β-il-acetat (12), u različitim prinosima u zavisnosti od upotrebljenog reagensa. Takođe, diskutovana je stereohemija 1β,6β-ciklizacionog proizvoda 13, nastalog intramolekulskom ciklizacijom 1,5-diokso-5,10-seko jedinjenja 12 na silika gelu

Kiselo-katalizovana i fotolitička reaktivnost nekih nezasićenih B-nor-5,10-sekosteroidnih ketona

The acid-catalyzed reaction of (Z)- and (E)-B-nor-5,10-seco-ketones 2 and 3 resulted in an intramolecular cyclization to give the 5-hydroxy-A-nor-1β,5β-10(19)-methylidene derivative 8, the 5β-hydroxy-A-nor-1(10)-unsaturated compound 9 and the 5β,10β-dihydroxy A-nor-product 10, from the (Z)-isomer and the 5-hydroxy-A-nor-1β,5β-10(19)-methylidene product 11, from the (E)-isomer. Upon UV-irradiation, the (Z)- and (E)-seco-ketones 2 and 3 underwent a reversible (Z)/(E) and (E)/(Z)-isomerization and in addition to a transannular photocyclization to afford the 10(19)-methylidene derivatives 8 and 11, respectively, while photolysis of the 10(19)-methylidene-B-nor-5,10-seco-ketone 4 gave the oxetane derivative 12.Kiselo-katalizovana reakcija (Z)- i (E)-B-nor-5,10-seko-ketona 2 i 3 rezultuje u intramolekulskoj ciklizaciji dajući 5-hidroksi-A-nor-1β,5β-10(19)-metilidenski derivat 8, 5β-hidroksi A-nor-1(10)-nezasićeno jedinjenje 9 i 5β,10β-dihidroksi-A-nor-proizvod 10, iz Z-izomera, i 5-hidroksi-A-nor-1β,5β-10(19)-metilidenski proizvod 11, iz E-izomera. (Z)- i (E)-Seko- ketoni 2 i 3 UV-ozračivanjem podležu reverzibilnoj (Z)/(E) odnosno (E)/(Z) izomerizaciji, kao i transanularnoj fotociklizaciji dajući 10(19)-metilidenske derivate 8 odnosno 11, dok se fotolizom 10(19)-metilidenskog-5,10-seko-ketona 4 gradi oksetanski derivat 12

Oksidacija holesta-5,8-dien-3β-il acetata sa perkiselinama

Expoxidation of cholesta-5,8-dien-3β-yl acetate (1) with peracids takes place preferentially at the more highly substituted Δ8-olefinic double bond to give: (a) with monoperphthalic acid, 8α,9α-epoxycholest-5-en-3β-yl acetate (2) (in 39 % yield) and 9α-hydroxy-5α,6α-epoxycholest-8(14)-en-3β-yl acetate (3) (in 30 % yield); and (b) with m-chloroperbenzoic acid, the 8α,9α-epoxide 2 (64 %) and 5α,6α-epoxy derivative 3 (20 %). Some chemical transformations of the obtained epoxides are described.Epoksidacija holesta-5,8-dien-3β-il acetata (1) sa perkiselinama prvenstveno se odvija na više supstituisanoj Δ8-olefinskoj dvoguboj vezi pri čemu se dobija: (a) sa monoperftalnom kiselinom, 8α,9α-epoksiholest-5-en-3β-il acetat (2) (u prenosu od 39 %) i 9α-hidroksi-5α,6α-epoksiholest-8(14)-en-3β-il acetat (3) (u prenosu od 30 %); i (b) sa m-hlorperbenzoevom kiselinom, 8α,9α-epoksid 2 (u prenosu od 64 %) i 5α,6α-epoksi derivat 3 (u prenosu od 20 %). Opisane su i neke hemijske transformacije dobijenih epoksida

Stereochemically Controlled Acetalizations in the Ten-Membered Ring of (Z)- and (E)-5,10-Seco-Steroidal Ketones

(Z)-3~-Acetoxy-5,10-seco-cholest-l(10)-en-5-one2a reacts with m-chloroperbenzoic acid to give the cis-(lS,10R)-epoxide 4, which, under acid-catalyzed conditions, undergoes stereospecific intramolecular cyclization to afford the (lS,5S,10S)-acetal 5. On the other hand, hydrolysis of the osmate ester of (E)-3~-acetoxy- -5,10-seco-cholest-1(10)-en-5-one 3a (with aqueous hydrochloric acid in methanol solution) produces two stereochemically different acetal derivatives, i. e. the (1R,5R,10R)-product7 and (1S,5S,10S)- -isomer 5, in ca. 49% and 28°/1 yields, respectively. The stereochemical course of these transformations is discussed in terms of the most stable ground-state conformations of the starting (Z)- and (E)-seco-ketones (2a and 3a) in solution

Fotohemijsko i Bekmanovo premeštanje(z)-holest-4-en-6-on oksima

Beckmann rearrangement of (Z)-cholest-4-en-6-one oxime (4) (prepared in 4 steps starting from cholest-5-en-3β-ol ο1)) with thionyl chloride in dioxane solution afforded an enamide-type lactam, i.e. 7-aza-B-homocholest-4-en-6-one (6) as a single product. Photoreaction of the same compound in methanol or benzene-acetic acid solution gave a mixture of products, with the formation of the parent ketone 3 and the occurrence of Z/E isomerization, while the lactam 6 was obtained only when the reaction was performed in methanol and then in very low yield (7%).Bekmanovo premeštanje (Z)-holest-4-en-6-on oksima (4) (koji je dobijen u 4 faze, polazeći od holest-5-en-3 β-ola (1)) sa tionil-hloridom u dioksanskom rastvoru, kao jedini proizvod daje laktam enamidnog tipa, tj. 7-aza-B-homoholest-4-en-6-on (6). Fotoreakcijom istog jedinjenja u metanolu ili u rastvoru benzen-sirćetna kiselina, nastaje smesa proizvoda koju čine polazni keton 3 i proizvodi Z/E izomerizacije, dok je laktam 6 dobiven u vrlo niskom prinosu (7%) samo u metanolnom rastvoru

Synthesis of 5-azaandrostane-3β,17β-diol protected at the 17β-hydroxyl group

In the present paper, the preparation of 3β-hydroxy-17β-dimethyl- tert-butylsilyloxy-5-azaandrostane (15) in fourteen steps is described. B-nor-17-oxoandrost-5-en-3β-yl acetate (1) 1,2 was used as the starting material, which was transformed to the key intermediate of the synthesis, B-nor-17β-dimethyl-tert-butylsilyloxyandrost-4-en-3β-yl acetate (7)

Kristalna struktura 14-okso-13,14-seko-5α-holest-13(18)-en-3β-il-acetata i određivanje konfiguracije njegovih acetoksi derivata

The crystal structure of 14-oxo-13,14-seco-5α-cholest-13(18)-en-3β-yl acetate (2), obtained (in addition to the (E)-Δ12-isomer 3) by oxidative fragmentation of the C(13)-C(14) bond of 14α-hydroxy-5α-cholestan-3β-yl acetate (1), was determined by X-ray analysis. In addition, the configurations of the acetoxy derivatives 4-6, formed by the thermal lead tetraacetate oxidation of 1, were deduced from the relevant 1H-NMR parameters.Kristalna struktura 14-okso-13,14-seko-5α-holest-13(18)-en-3β-il-acetata (2). koji se dobiva (pored (E)-Δ12-izomera 3) oksidativnom fragmentacijom C(13)-C(14) veze 14α-hidroksi-5α-holestan-3β-il-acetata (1) određena je analizom X-zraka. Pored toga, konfiguracije njegovih acetoksi derivata 4-6, koji se grade pri termičkoj olovo-tetraacetatnoj oksidaciji, izvedene su na osnovu odgovarajućih 1H-NMR parametara

Transannular Photocyclization of (E)-3B-Acetoxy-5,10-seco-1(10)-cholesten-5-one*

UV irradiation of the (E)-5,10-seco-steroidal ketone 1 in acetone solution results, in addition to the previously describedE/Z isomerization and intramolecular Paterno-Buchi reaction(leading to the la,5:x-oxetane 4 in about 42% yield and 1~,5~-oxetane5 in 2-3% yield), in atransannular cyclization (accompaniedby acetic acid elimination) producing the anthrasteroidal enone 3 (in about 7% yield). The structureof 3 was deduced from spectral data and confirmed by X-ray analysis