Studien in der Vitamin D‐Reihe XV: Neue Aufbaumethode für 9.10‐seco‐Steroide mit dem Triensystem des Tachysterins

Abstract

Durch Wittig‐Kondensation von 2‐Methyl‐cyclohexen‐(1)‐aldehyd‐(1) mit Triphenyl‐[cyclohexen‐(1)‐yl‐methylen]‐phosphin konnte erneut der Modellkohlenwasserstoff mit dem Triensystem des Tachysterins in hoher Reinheit gewonnen werden.

Photochemistry of Structural Analogues of Previtamin D3: Generality of the Wavelength-Dependent Triene Photocyclization

“…Trienes 1 and 2 were obtained by convergent synthesis. A mixture of cis - and trans -1,2-di(1-cyclohexenyl)ethene were obtained in the reaction of 1-cyclohexenylcarbox-aldehyde5a ( 3a ) with triphenyl(1-cyclohexenylmethyl)phosphonium bromide in the presence of n BuLi. The pure cis isomer 1a was obtained either by column chromatography of the mixture of cis and trans isomers or by photochemical sensitization of trans isomer 1b with 9-fluorenone.…”

“…trans-1,2-Di(1-cyclohexenyl)ethene (1b). 1-Cyclohexenylcarboxaldehyde 5a (3a) (3.0 g, 27 mmol) was added to a solution of triphenyl(1-cyclohexenylmethyl)phosphonium bromide 6 (4) (9.0 g, 21 mmol), n-butyllithium (11 mL, 2.3 M in hexane, 25 mmol), and THF (40 mL) with stirring at 0 °C. The reaction mixture was refluxed for 3 h, and then water was added.…”

“…Trans isomer: IR νmax 2950, 1644, 1459, 1448, 1141, 962 cm -1 ; 1 H NMR δ 1.62 (m, 8H), 2.14 (m, 8H), 5.73 (m, 2H), 6.13 (s, 2H); 13 C NMR δ 22. 6,22.7,24.6,26.0,128.6,128.8,136.0,MS m/z 188,145 (base),117,105,91,77; UV λmax ( ) 259 (20 570), 268 (24 900), 280 (20 000).…”

“…). 6 The reaction procedure was as described above. 2-Methyl-1-cyclohexene carboxaldehyde 5b (3b) (0.9 g, 7.3 mmol) was allowed to react with (1-cyclohexenylmethylidene)triphenylphosphorane to give trans-2-(1-cyclohexenyl)-1-(2-methyl-1-cyclohexenyl)ethene (0.8 g, 55%): IR νmax 2950, 1643, 1468, 1459, 1144, 961 cm -1 ; 1 H NMR δ 1.63 (m, 8H), 1.77 (s, 3H), 2.14 (m, 8H), 5.76 (m, 1H), 6.19, 6.61 (AB quartet, 2H, J ) 16 Hz); 13 C NMR δ 19.4,22.6,22.7,22.9,23.0,24.6,25.5,26.1,33.1,123.6,127.9,128.6,129.0,132.7,136.4;MS m/z 202,187,159,145 (base),131,117,91,77;UV λmax ( ) 268 (34 310),278 (42 100),289 (31 750).…”

A + Cd → Acd → Abcd

“…Inhoffen [35,36], in his studies on vitamin D derivatives, and Lythgoe [37,38], in analogous work on the synthesis of calciferol and its derivatives, briefly studied the use of appropriate phosphoranes in preparing secosteroids; however, they found other modes of attack more satisfactory. Interest in the reaction, as applied to steroid total synthesis, has been revived by a Russian group, and their work, culminating in the total synthesis of di-estrone methyl ether, is presented in Scheme 7-8.…”