Vol. 77
NOTES
5438
Furo-chromones and -Coumarins. XIII. The Dicoumarol Analogs of Bergapten, Isopimpinellin and Pimpinellin BY ALEXANDERSCHOSBERG, SASRY BADRAN ASD XICOLAS A . STARKOKSKI' J U X E 1, 1955 RECEIVED
*is bergapten (Ia), isopimpinellin ( I b ) and p i x pinellin (11)are substances of known physiological action (comp. the photodynamical action of Ia,' the molluscicidal action of I a and Ib,2and the well known poisonous character of these three natural furocoumarins to fish3), and as dicoumarol is an anticoagulant of great medical interest, i t seemed advisable to prepare the dicoumarol analogs of the mentioned furocoumarins. OCHI
ethyl carbonate
~.
1
Sa
OCHi I
IZ
L,
R
h, R = OCHi
. -
Ia, R = H b, R = OCHa
I1
(ICHn
The synthesis of these derivatil-es of dicoumarol starting with the corresponding coumarins is impossible, or a t least very difficult. IVe have found a suitable way starting with visnagin ( I I I a ) and khellin (IIIb), two natural chromones which are now easily available from the Egyptian plant Ammi uisnaga (L.), and isokhelfin (IV) prepared synthetically from khellin.4 As an example, the synthesis of 3,3'-methylenebis-(4-hydroxy-5-rnethoxyfuro-4',3',6,7 -coumarin) (IXa) from visnagin (IIIa) has been carried out as follows.jS6 *In analogous series of reactions starting with isokhellin ( 1 1 7 ) yields the dicoumarol derivative X. While the alkaline hydrolysis of visnagin (IIIa) to visnaginone (Va) and of khellin (IIIb) to khellinone (Vb) are already known, i t seems t h a t the hydrolysis of isokhellin (117) to isokhellinone (VI ) has not yet been published. The new 4hydroxycoumarin derivatives VIIa and VIIb have been methylated with methyl iodide in the presence of acetone and potassium carbonate. Ailthoughthe methylation of 4-hydroxycoumarins by this method has been reported to give the 4(1) H. Kuske, .4uch. D t r u i . S r p h . , 176, 112 (1938); L. blusaju, G. Rodighiero and G. Caporale, Bull. soc. chim. bioi., 3 6 , 1213 (1954). ( 2 ) A . Schonberg and N . Latif, THISJ O U R N A L , 76, 6208 (1954). ( 3 ) E . Spath and F. Kuffner, .Vfortatsh, 69, 75 (1936) ( 4 ) J . R . Clarke and A . Robertson, J . Chem. Soc., 302 (1949); S. K . Mukerjee and T . R . Seshadri, J . S c i . I n d . Research ( I n d i a ) , l S B , 400 (1954). ) Coinp. J. Boyd and A. Robertson, J . Cheiii. Sec., 174 (1948). ) V
