[CONTRIBUTION FROM
THE
STERLING CHEMISTRY LABORATORY, Y A L E UNIVERSITY ]
COXTRIBUTIONS TO T H E STUDY OF MARINE PRODUCTS. XVI. 7-DEHYDROCLIONASTEROL WERNER BERGMANN, A. M. LYON,
AND
MARGARET J. McLEL4N
Received March 3, 194.6
Heilbron (l), and Bock and Wetter (2) have shown by spectrographic and chemical means that sterols of invertebrates are as a rule considerably richer in 7-dehydrosterols than the sterols which have so far been isolated from vertebrates. In a few instances (2) the 7-dehydrosterols of invertebrates have been isolated and identified as 7-dehydrocholesterol or ergosterol. As yet very little is known about the 7-dehydrosterols of sponges. In the case of the marine sponge, Spheciospongia vesparia, the presence of a small amount of 7-dehydrosterol was indicated by spectrographic evidence (3). Of greater significance is the work of Mazur (4) who by chromatography isolated a sterol fraction from the fresh-water sponge Spongilla which contained 56% of 7-dehydrosterol. In connection with certain studies on the sterols of sponges it became desirable to have available a sample of a 7-dehydrosterol which might conceivably be present in sponges. Since clionasterol is one of the more common sterols found in sponges ( 5 ) it appeared reasonable to assume that 7-dehydroclionasterol might be present in the same source material, and for this reason a preparation of this substance was carried out by the conventional procedure. Clionasteryl acetate was oxidized to 7-ketoclionasteryl acetate (G), which was then reduced by aluminum isoproposide to the mixture of 7-hydrcxyclionasterols. In one series of experiments, benzoic acid was split out of the dibenzoates of the diols by heating with dimethylaniline according to the method of Haslewood (6). The monobenzoate thus obtained mas then hydrolyzed to give 7-dehydroclionasterol. Better results were obtained in the second series of experiments where the dibenzoates were first hydrolyzed according to Wintersteiner and Ruigh ('7) to give the isomeric 7-benzoxyclionasterols, from which benzoic acid was then removed with boiling dimethylaniline. The 7-dehydroclionasterol thus formed was isolated 2s its digitonide, and the latter converted directly into 7-dehydroclionasteryl acetate with acetic anhydride. The absorption spectrum of the acetate mas identical with that of ergosteryl acetate, log 6 2 8 2 = 4.04. EXPERIMENTAL
All melting points are corrected. All optical rotations were taken i n a 1-dm. tube, the sample being dissolved in 3.0 cc. of chloroform. 7-Ketoclionasteryl acetate. A solution of 17.2 g. of chromic anhydride in 160 cc. of glacial acetic acid and 5 cc. of water was added dropwise over a period of 150 minutes t o a well stirred solution of 20 g. of clionasteryl acetate in 200 cc. of acetic acid. During the addition and for four hours afterwards the solution was kept a t 60-65". The excess chromic anhydride was then reduced by alcohol, and the solution concentrated in vacuo t o a small volume. Water was then added and the mixture extracted with ether. The ether extract was washed with alkali and water, dried over anhydrous sodium sulfate and evaporated t o 290
7-DEHYDROCLIOKASTEHOL
29 1
dryness. The residue after four recrystallizations from ethanol gave 4.0 g. of 7-ketoclionasteryl acetate of m.p. 172-173", [CY]:-99.44" (6.10 mg., CY -1.92"). AQaZ. Calc'd for CS1H~003:C, 79.10; H, 10.70. Found: C, 79.10; H, 10.98. 7-Hydrozyclionasteryl dibenzoate. A solution of 4 g. of 7-ketoclionasteryl acetate in 60 cc. of anhydrous isopropanol was treated with 3.5 g. of aluminum isopropoxide. The solution was then heated under a fractionating column until the distillate no longer gave a nitroprusside test for acetone. One hundred cc. of a 770 aqueous solution of potassium hydroxide !".as then added t o the solutionin the distilling flask, and the solid material whichprecipitatetl was filtered, washed, and dissolved in ether. The washed and dried ether solution was then concpntrated t o a small volume and diluted with 200 cc. of low-boiling petroleum ether. Upon cooling, 1.2 g. of n crystalline diol, m.p. 153-158", was obtained. Concentration of the mother liquor gave the lower-melting epimer. One grain of the diol of m.p. 153-158" was benzoylated in pyridine in the usual manner. There was (obtained 1.2 g. of a dibenzoate, which after four recrystallizations from acetonemethanol formed nice needles and melted a t 159-160", [CY];+93.4" (46.4 mg., a 4-1.45'). A n a l . Calc'dfor C43HS804:C, 80.S3; H , 9.15. Found: C, 80.70; 13, 8.91. The lower-melting diol gave 1.2 g. of a benzoate of m.p. 135-145". 7-Dehydroclionasteryl benzoate. A solution of 0.5 g. of the dibenzoate of m.p. 159-160" i n 5 cc. of freshly distilled dimethylaniline was refluxed for eight hours. The solution was then poured into dilute hydrochloric acid, and the precipitated material was extracted with ether. The ether extract was washed with water, dried, and evaporated t o dryness. Recrystallizai ion of the residue from absolute ethanol gave 0.21 g. of 7-dehydroclionasteryl benzoate which melted t o a turbid liquid a t 133-135" and turned clear a t 138". A n a l . Calc'd for C ~ ~ H ~ QC, OZ 83.67; : H, 10.14. Found: C, 83.32; H, 10.04. When treated in the same manner, 1.2 g. of the lower-melting benzoate gave 0.2 g. of 7dehydroclionasteryl benzoate. 7-Dehydroclionasterol. A solution of 0.4 g. of 7-dehydroclionasteryl benzoate in 50 cc. of ether was added dropwise t o 25 cc. of a boiling 274 solution of potassium hydroxide i n methanol. The ether was distilled off slowly while a stream of nitrogen was passed through the solution. The solution was then cooled, and the crystalline material which settled out was filtered, washed with water and methanol, and recrystallized from absolute ethanol. It formed glistening plates and melted at 138", [a]: -98.2" (18.6 mg., a -0.61"). The 7dehydroclionasterol was rather unstable and turned yellow on standing. A n a l . Calc'd for C2i"80.0.5 HzO: C, 82.59; H , 11.71. Found: C, 82.47; H, 11.54. 7-Dehydroclionasteryl acetate. To 0.4 g. of 7-hydroxyclionasteryl dibenzoate dissolved i n 8 cc. of benzene, a solution of 0.26 g. of sodium methoxide i n 13.5 cc. of anhydrous methanol was added, and the mixture was allowed t o stand at room temperature for one day. It w:as then poured on cracked ice, and the benzene layer was washed several times with cold water. Evaporation of the benzene solution gave an oil, which was a t once refluxed with 10 cc. of freshly distilled dimethylaniline in a n atmosphere of carbon dioxide for three hours. The solution was then cooled, diluted with ether, and freed from dimethylaniline by thorough extraction with hydrochloric acid. A spectrographic assay of the ether solution indicated a yield of 67% of 7-dehydroclionasterol. The ether solution was then evaporated t o dryness i n a n atmosphere of carbon dioxide, and t h e residue was dissolved i n 90% ethanol and precipitated with a 1%solution of digitonine. The digitonide, 0.68 g., was refluxed for thirty minutes with 10 CC. of acetic anhydride, and the 7-dehydroclionasteryl acetate which separated on cooling was recrystallized sever,d times from ether-methanol. It melted a t 139-140", [a]: -71.6" (15.5 mg., a -0.37"). Log ~ 2 8 2= 4.04. A n a l . Calc'd for C31H~02:C, 81.88; H, 11.10. Found: C, 81.68; H, 11.14.
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BERGMANN, LYON, AND MCLEAN SUMMARY
A preparation of 7-dehydroclionasterol and some of its derivatives has been described. NEW HAVEN,CONN. REFERENCES GILLAMAND HEILBRON, Biochem. J.,30,1253 (1936). BOCKAND WETTER,2.physiol. Chem., 256.33 (1938). VALENTINE AND BERGMANN, J . Org. Chem., 8,452 (1941). MAZUR,*J. Am. Chem. Soc., 63, 883,2442 (1941). WUNDERLICH,2. physiol. Chem., 241, 116 (1936). (6) HASLEWOOD, J . Chem. Soc., 224 (1938). (7) WfNTERSTEINER AND RUIGH,J . Am. Chem. SOC., 64,1177 (1942). (1) (2) (3) (4) (5)
