July 5 , 19.55
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COMMUNICATIONS TO THE EDITOR
atoms away from ring A and toward ring E. Consideration of friedelin as a possible rearrangement product of a- or p-amyrin prompted us to undertake the experiments which are outlined $,"dfi3,a~t~:,orc~o in this report and which have led to the direct correlation of friedelin with 6-amyrin.
IX
lupeol (VI)5 into friedelin by a sequence of 1,2shifts would lead not only to the correct carbon skeleton, but also to the experimentally established stereochemical configuration a t all asymmetric centers and to the p-orientation of the hydrogen a t C18 (D/E cis) as in a 6 - and B - a m ~ r i n . ~For this
CH CH3
R = H, Friedelin (V, D / E cis) R = OH, cerin
iriedelin(eno1)
3amy rin
Reduction of friedelin with lithium aluminum reason we favor the view that the hydrogen a t CISin hydride produces friedelan-35-01 (11), m.p. 283.5- friedelin is p-oriented.R 285°,2*3in which the hydroxyl function is axial. If the above biosynthetic pathway is correct, two Treatment of I1 with hydrogen chloride in phenol sequences for formation of pentacyclic triterpenes a t 110" causes a remarkable multi-group rear- follow: (1) lupeol + p-amyrin -+ friedelin and rangement which affords olean-l3(lS)-ene (111) (2) lupeol -+ a-amyrin presently unknown rela(55% yield), m.p. 186-187', [ a ] -~12.5' (C, 0.80, tive of friedelin. We are currently engaged in a chloroform), A,, 213 mb (log E 3.51), bright yellow search for the missing a-amyrin analog of friedelin coloration with tetranitromethane, Anal. Calcd. as well as for other intermediates in both series. for C30Hb0:C, 87.73, H, 12.27. Found: C, 87.76, The formulation of cerin as 26-hydroxy friedelin H, 12.37. This material is identical with an authen- follows from the location of the hydroxyl a t C2 and tic sample prepared from 6-amyrin by oxidation, from the fact t h a t the hydroxyl is very easily acylWOE-Kishner reduction and acid-catalyzed isom- ated or sulfonated (equatorial orientation). erization of the 12,13-double bond to the 13,18-p0I n connection with the work in this and the presition, m.p. 186-1237" (undepressed upon admixture with a sample from rearrangement of freidelan-3p- ceding paper, we wish to express our thanks to Dr. ol), [ a I 2 j -13.9' ~ (C, 0.79, chloroform) bright I. H. Riley for the X-ray measurements, to Dr. R. yellow coloration with tetranitromethane. The in- A. Sneen for the deuterium analyses, to Messrs. frared spectra of the above samples of A13(18)-olefin H. C. Huang, D. F. Joesting and R. G. Schultz for are identicaL4 Further confirmation of identity help in isolation of friedelin and preparation of was obtained by conversion of both products to the intermediates, to the Armstrong Cork Company for same mixture of epimeric oxides with perbenzoic supplies of cork wax and to the Eli Lilly Company acid, m.p. ca. 191-5", undepressed upon admixture. for generous financial support. See L. Ruzicka, A. Eschenmoser and H. Heusser, E x p e r i e n l i n , 9 , Both samples of oxide upon treatment with boron 357(5)(1953). trifluoride ethereate yielded olean-1 1, 13(18)-diene (6) E. J. Corey and J. J. Ursprung, Chem. and Znd , 1387 (1854). (Iv)4,m.p. 219-220") [ a ] * j D -72.4' (c, 0.95, (7) D. H. R. Barton and N. J. Holness, J . Chem. Soc., 78 (1952). (8) This view is confirmed b y a 2-dimenqional F o u t i e r X-ray analysis chloroform), Amax 242, 250, 260 mp (log E 4.44, 4.50, friedelan-3a-01 chloro and brornoacetates made in these Laboratories 4.31), A n d . Calcd. for C30H48:C, 88.16, H, on by Dr. I. E. Riley, the results of which are completely concordant with 11.84. Found: C, 85.02; H, 11.91,browncoloration structure V ( D / E cis) for friedelin. These results will be reported later. with tetranitromethane, mixture m.p. undepressed. DEPARTMENT OF CHEMISTRY --f
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I1
X
111
CHEMICAL ENCINEERISC E. J . COREY UNIVERSITY OF ILLINOIS J. J. URSPRUNC URBANA,ILLINOIS RECEIVED MAY 19, 1955 AND
LUMINESCENCE SPECTROSCOPY OF PORPHYRINLIKE MOLECULES INCLUDING T H E CHLOROPHYLLSI
The conversion of I1 into I11 proves the location of methyl groups a t C1, and CZO as in P-amyrin and, together with the degradative work, establishes beyond any doubt structure V for friedelin, which is complete except for the orientation of the hydrogen a t Cis. The biosynthetic pathway for the conversion of
Sir: The understanding of the participation of the chlorophylls in the primary reaction of photosynthesis demands an exact knowledge of the location and characteristics of the lowest excited states of these molecules.2
(2) J. J. Lander and W. J. Svirbely, THISJOURNAL, 66, 235 (1944). (3) Recently isolated from various natural sources by P. R . Jefferies, J. Chcm. Soc., 473 (1954). and by T. Bruun, Acta Chcm. Scond., 8 , 71 (1954). (4) K. Takeda, J . Pharm. SOC.J a f i a n , 63, 197 (1943); C. A , , 45 586 (1951).
(1) Work done under a contract between t h e Office of Naval Research, U. s. N a v y , and t h e Florida State University. (2) R. S. Becker and M. Kasha, "Luminescence Spectroscopy of Molecules and t h e Photosynthetic System,'' Conference on Luminescence, Pacific Grove, California, March 29, 1954, National Research Council Bulletin, in press.
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COMhll’NIC.4TIONS TO THE
EDITOR
Vol. 77
in chlorophyll-n (;.e., 0)and in chlorophyll-b ( 2 0.1I observed in dilute rigid glass solution a t low ternperatures does not rule out the lowest triplet state from participation in the photosynthctic reaction. -411 observations were made using ;t Steinheil Universal Spectrograph GH, with f 3 coated glass optics, using three large coated glass prisms. The exciting light was the rZH-6 high-pressure 1 kw. water-cooled mercury arc, inonochromatized by suitable filters. Both steady excitation with filtered light, and intermittent excitation with a phosphoroscope of IO-&sec. resolving time was used. In the case of Ni’-L and C u + + derivatives, only steady excitation yielded emission, indicating the shortening of T + S emission lifetime by the strong spinorbital coupling in those compounds. In the case of phthalocyanines, no phosphorescence was observed in the photographic infrared up to 9000 A . , it appears that the lowest triplet states of these molecules lie a t longer wave lengths. I n the case of the metal derivatives of etioporphyrin-11, the strong fluorescence of the parent compound was partially quenched with consequent enhancement of phosphorescence”.’ in the Zn- derivative, while in the S i - ’ and C u + + complexes only (strong) phosphorescence was observed, :IS expected for strong spin-orbital coupling. .I complete discussion of the above results and the publication of the spectra obtaiiietl will be preTABLE I sented in a forthcoming paper. LUMIYESCESCED A T A O N P’ORPHLXIS-LIKE ~ ~ O L E C U L E S The , recent observations by Livingston, et al.,’ ( ~ L L IS EPA GLASS“ AT 77°K.) on the transient absorption originating in excited \Vave length of first strong band, A. chlorophyll molecules is thus most probably the Molecule b’luorescence Phosphorescence triplet-triplet absorption, in accordance with simiEtioporphyrin-11 6236 8060 lar observations made on other molecules.1o Zn ++-Etioporphyrin-I1 5730 7000 (9) K. Livingston a n d v. A . Kyan, ’THIS J O U R N A L , 7 6 , 2176 ( l Y 3 3 ) ; Cu +-Etioporphyrin-I1 Sone 6812
The low temperature light emission properties of several metallo-derivatives of phthalocyanines, porphyrins and chlorophylls have been studied. The lowest triplet-singlet emissions of the latter two groups of molecules have been located and shown to be in accord with expected behavior based on spin-orbital perturbations introduced by heavy and paramagnetic atom^.^,^,^ The results are summarized in Table I. The phosphorescence of chlorophyll-b was reported earlier by Calvin and Dorough,6,ibut could not be duplicated by later work.’ Our work provides proof that the phosphorescence of chlorophyll-b reported earlier is a bona$de emission. SYe observed a phosphorescence in chlorophyll-b with a first strong band at 8650 A. (0,O-band a t 11618 cm. - I ) , using two chromatogrammed saniples from different sources. Using pheophorbide-ci as an analog of chlorophy!!, we showed that its strong fluorescence (6701 A,, first band) is converted completely to phosphorescence in Cu ++pheophorbide-a. Moreover, the phosphorescence occurs at 8675 -1. (first strong band). This complete conversion in the presence of a paramagnetic ion, and the position of the emission, indicate that the phosphorescence observed in the pheophorbide and the chlorophyll are the lowest triplet -+ singlet emissions in these molecules. 3,5
+
+
S i +-Etioporphyrin-I1 hTone 6812 Phthalocyanine 6918 S o t obsd. M g +-Phthalocyanine 67(J5 S o t obsd. Zn ++-Phthalocyanine 6731 S o t obsd. Pheophorbide-a 6701 Sone found Cu ‘-Pheophorbide-e Sone 8675 Chlorophyll-a 664Sb None fount1 Chlorophyll-b 6564 8t%O Chlorophyll4 64 8jb .. G. S . Lewis and D. Lipkin, THISJov (19-12). Rootn temp. i n ether solution, F. Harris, J . P h y s . Chem., 47, 623 (1943). +
+
Phosphorescence was not found in chlorophyll-a, and that observed in chlorophyll-b was relatively weak, indicating a quantum efficiency of the order of magnitude of 0.1 or less under the conditions studied. However, in Cu++-pheophorbide-a the quantum yield of phosphorescence is probably close to unity, as the emission was relatively intense. X detailed consideration of the role of chlorophyll in photosynthesis must include the possibility of strong inter-molerdcir spin-orbital perturbations. Thus, the low yield of phosphorescence (3) A I Kaaha, I : c ~ r u h y.Sic, Disrtrrziori, Y-n 9 , 1-1 (1950). (4) D. S . XIcClurr. J . Chein. P h , s , 17, 90.5 (1949). ( 5 ) P. Yuster and S . I. Weissman. tbid., 17, 1182 (1949). ( 0 ) XI. Calvin and G. Dorough, S c i e n c e , 1 0 5 , 433 (1947). (7) A I , Calvin and G. Dorough, THISJ O U R N A L , 7 0 , 899 (1948). ( 8 ) K. Livingston, “The Photochemistry of Chlorophyll,” p. 179196, in “Photosynthesis in Plants,” edited by J. Franck and W. E. Loomis. I o w a State College Press, Ames, I o w a , 1949.
R . Livingston, G Porter and XI. LV n’indsnr, K. Livingston, THISJ O I J R N A L , Ti’, 2179 i l R 5 S l . 110) G . Porter and A I . \V, XX’indwr, .I. C h e n . Pit?s , 2 1 , 2088 (1058).
DEPARTMENT OF CHEMISTRY FLORIDA STATEUSIVERSITY TALLAHASSEE, FLORIDA RECEIVED MAY26, 1 9 5
R.S. BECRER hf.
KASHA
A WATER SOLUBLE SYSTEMIC INSECTICIDE 0,ODIETHYL S-2-ETHYLMERCAPTOETHYL PHOSPHOROTHIOLATE METHOSULFATE Sir :
I n connection with studies concerning the chemistry and toxicology of the thiono- and thiol-isomers of Systox,’ we have prepared and measured the insecticidal activity of 0,O-diethyl S-?-ethylmercaptoethyl phosphorothiolate methosulfate (methosulfate of the thiol isomer). The product was obtained by heating equimolar amounts of 0,O-diethyl S-2-ethylmercaptoethyl phosphorothiolate,2 b.p. 106-108” (0.3 mni.), n% 1.49%, and freshly distilled methyl sulfate on the steambath for one hour.3 The phosphorothiolate (I) Systox is the trade name given by the Clicrnasro Corp., N e w York, K . Y . , for a technical mixture of O,O-dlethyl 0-2-ethylmerca1itoethyl phosphorothionate and O,O-diethyl S-2-ethylmercaptuethyl phosphorothiolate. ( 2 ) G. Schrader, “Die Bntwicklung neure Insektizide auf Grundlage organischer Fluor und P h o s p h o r - ~ ’ e r h i n d u n g e n , ”Alono&ral,h N o . 6 2 , Angewiindte Chemie, 19.52. ( 3 ) I . 4 . Usov, >I 2. .Finkelshtein and V. pi. Belov, J . C r n . Chrm. (U.S.S.R.), 17, 2253 (1947).
