5388
RODERICK A. BARNESAND MICHAELT. BEACHEM
[ CONTRIBUTIUS FROM
THE SCHOOL O F CHEMISTRY,
RLTGERS UKIVERSITY, THESTATE
V U I . '77
USIVERSITY OF S E \ V JERSEY
1
T h e Stereochemistry of 4a-Methy1-1,2,3,4,4a,9,10,10a-octahydrophenanthrene BY RODERICK A. BARNES AND MICHAEL T. BEACHEM' RECEIVED OCTOBER13, 1954 'l'hc. configuratioiis of the cis aiid trans forms of 3a-inethyl-1,2,3,1,4a,9,lO,lOa-octah~dropher1a1ithrci1e have bccii estaliliihed by degradatioti t o the kiiowii isomers of 2-methyl-2-carboxycyclohexaneacetic acid. Definite proof was ohtaiiieti i i i this way that the major product from the sulfuric acid cyclization of 1-~-phenyleth~-1-2-niethylcyclohexatiol was the cis izoiner. A minor product, previously believed to be a spiraiie, iiow has been proved t o be the trans isomer; thereforc this particular cyclization is not wholly stereospecific 17-ith a ratio of cis to trans forms of approximately four t o one.
I n a previous publication? i t was reported t h a t Thus the trans isomer was present not only in the major product resulting from the cyclization the cyclization product obtained in the present of 1-~-phenylethyl-2-methyl-l-cyclohexanol was one work but also in the product previously reported. of the isomers of 4a-rnethyl-l,2,3,4,4a,9,1O,lOa-oc-The amount of trans isomer from the cyclization tahydrophenanthrene (Ia). On the basis of a with 85% sulfuric acid2 must be less than 20% mechanism for the cyclization of P-arylethylcyclo- since 76% of the total cyclized product was the hexanols which has been p r o p ~ s e dthis , ~ isomer was pure cis isomer and the remaining 24% was a inixassigned the cis configuration. The purpose of ture of both isomers. The cyclization with goc/;, this research was to establish definitely whether sulfuric acid yielded more of the trans i s o ~ n e r ~ ; or not this cyclization product was actually the ci\ an increase in the amount of trans isomer under more drastic cyclization conditions is in accord isomer. The first step in achieving this goal was the with the theoretical prediction. preparation of 9-ket0-4a-inethyl-l,2,3,4,4a,9,10,1 OaThe structure proof plan next required that the octahydrophenanthrene (11). oximes IIIa,b of ketones I1 be carried through a Beckmann rearrangement. Polyphosphoric acid' fi
Ia,h
IIa,b
LVhen distilled, but unfractionated, hydrocarbon I was used for the oxidation to ketone 11, there resulted rather unexpectedly a mixture of two ketones. These ketones were separated by fractional crystallization of their oximes and then identified as the cis and trans forms of I1 by conversion of the oximes to the known "4dinitrophenylhydrazones. ? # The product from a previous cyclization,' obtained in 85y0 yield, had been fractionated carefully to yield 7y0of uncyclized olefin, 71 % of pure cis isomer and 227, of material having a slightly higher refractive index than the major product. When this experiment was carried out it was thought that this latter material was a mixture of the cis isomer and a spirane. The basis for this belief was the observation t h a t fractional distillation was successful for the separation of a spirane from the isomeric 1,2,3,4,4a,9,10,1Oa-octahydrrtphenanthrenes,? while the cis and trans forms of this octahydrophenanthrene were reported to be inseparable by distillation.6 11-e now have proved that the fraction with the high refractive index n as actually a mixture containing both isomers of I. (1) Abstracted f r o m a thesis presented b y hS T. Hearhem t o the Graduate School for t h e P h I). Degree, June, 1951. ( 2 ) R . A. Barnes and R . T. Gottesnian. THISJ O U R N A L , 1 4 , 35 (1952). ( 3 ) R. A . Barnes, i h z 4 , 7 5 , 3004 (19.53). ( 4 ) R .4 U a r n r s a n < l LS I). K < l n o r t , ;hit/ , 7 5 , 30:3 i19.73) ( 6 ) D. Perlman, L). Davids-a &step procedure are given, the latter comprising three successive oxidation reactions, using selenium dioxide, chromic acid and hydrogen peroxide.
Bergapten ( I ) and visnagin (VII), which can he extracted together with the inedically important xanthotoxin and khellin from the Egyptian plants Ammi mujus (L.) and Ammi visizaga (L.), respectively, have now been used as starting materials in the synthesis of other products, namely, of some coumarins of the fraxinol group and some flavones of the baicalein g r o u p . In these syntheses, the key reaction W I S the easy oxidation of the furan ring of visnagiri (VII)'a and bergaptell (I)I b with chromic acid. This oxidation, which leads t o derivatives of salicylaldehyde, now has been extended also to a furoflavone (Xi prepared from visnagin. Synthesis of Fraxinol (IV) .--The methylation of upoxanthoxpletin (11), obtained by the oxidation ( I ) (a) I\. Scliirribcrg, S 1l;ulrau aiiil S. .I. St6trko!,hky, 'I'IIIS 103,)2(1953,; (I,) 77, 101!1 (l!l.j.j)
[ ( a i RN,~!,7 , 6,
of bergapten
( 1 ) ) ' b with methyl iodide and potassium carbonate in acetone, led to .i,7-dimethoxy-tiiormylcoumariii (111). Replacement of the fot-niyl group by a hydroxyl group by means of oxidation with hydrogen peroxide in sulfuric acid medium afforded 5,7-diinethoxy-G-hyclroxycoumarin(fraxinol) (11') in good yield. This substance has been synthesized previously on different lines.2-3 The c.ixidatioii of aposanthoxvletin (11) itself with dkalinc: hydrugcri peroxide lcd to 6,7-dihydroxy-5niethoxycoumarin (Vi, which has then been methylated to :J,B,7-trii7iethoxycouiii~riri(VI) E . Sp.hth and Z
J e r i m a n f , ~ r s k a - S i e n k i e . r i c z o w a ,lie,.., 70, (i98
