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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.

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.

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.

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.

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.