June 5 , 1959
COMMUNICATIONS TO THE EDITOR
2911
dichlorostyrene2 as the monomer pair, some variations in monomer reactivity ratios have been observed with different Lewis acid catalysts, although, since most of these polymerizations were heterogeneous, some of the variations may be due to surface effects. Stannic chloride and aluminum bromide were used as catalysts for homogeneous copolymerizations carried out in n-hexane, nitrobenzene and nitromethane at 0’. The monomers were mixed in predetermined proportions and added to the solvent, then after cooling, the catalyst. The total concentration of monomer was 20 mole yo in all cases. Polymerization times varied from 3 to 15 minutes, preliminary experiments with each system having indicated the times required for conversions to reach roughly 7%. The copolymer was precipitated by addition of methanol and purified by repeatedly dissolving in methyl ethyl ketone and precipitating by addition of methanol. The compositions of the copolymers were determined by analytical determination of their chlorine contents. For each system studied, the monomer reactivities rl and r2 (isobutylene = monomer 1 ; p-chlorostyrene = monomer 2) were calculated. The values obtained were: rl = 1.01, r2 = 1.02 for copolymerization in n-hexane using AIBr3 (0.5 mole %) as catalyst; rl = 14.7, r2 = 0.15 in nitrobenzene using AlBr3 (0.1 mole TO);rl = 22.5, r2 = 0.7 in nitromethane using AlBr3 (0.5 mole %) and r~ = 8.6, rz = 1.2 in nitrobenzene using SnCL (0.3 mole 70). No polymerization took place in n-hexane when SnC14was used as a catalyst. From these results i t can be seen that, in the systems studied, the monomer reactivities in the non-polar solvent differ very greatly from those in the polar solvents. Although several explanations can be offered for these results, i t is best to await further data. Such large variations have not been observed previously in ionic copolymerization systems in which homogeneity is retained during polymerization. Further work in this unique system is in progress. Acknowledgment.-We gratefully acknowledge the support given by a “Grant-in-Aid” from the Shell Development Company.
thesis of deoxyribo-oligonucleotides containing Ct,’-C3’ internucleotide bonds, no specific synthesis of corresponding compounds in the ribonucleoside series has hitherto been reported. The present communication outlines an approach which has been used successfully in the synthesis of uridylyl(5’+3’)-uridine (I) and offers promise for the synthesis of other ribo-oligonucleotides. Uridine-5’ phosphate was treated with dicyclohexylcarbodiimide under high dilution conditions to yield uridine-305’ cyclic phosphate (II), Rr 0.29,4 which was isolated after chromatography as the ammonium salt in 60% yield. The cyclic
(1) For nomenclature system see ref. 3a. (2) This work has been supported by a grant from the National Cancer Institute of the h-ational Institutes of Health, U. S. Public Health Service.
(5) G.W. Kenner, A. R. Todd, R . F. Webb and F. J. Weymouth, J . Chem. Sac., 2288 (1954). ( 6 ) L. A. Heppel and R . J. Hilmoe, “Methods in Enzymology,” Vol. 11, Academic Press, Inc., Kew York, N. Y., 1955, p. 565.
0
o=+’-O
OH
it-
0 H O - pII O C ~ o y U r
IV
OR
U
O=P-OH I OH V,R=H VI, R=(CeHj)$-C-
I - VI, Ur = Uracil
phosphate (11) as the free acid was treated with dihydropyran in anhydrous dioxane to give the 2’-O-tetrahydropyranyl derivative (111), Rr 0.55,4 quantitatively. Hydrolysis of 111 with sodium hydroxide gave a mixture of IV and V, which was treated directly in anhydrous pyridine with an excess of triphenylmethyl chloride. The resulting derivative (VI, Rf 0.6g4isolated in 30y0 yield based on TI) and unreacted IV, Rt 0.304, (10% yield from 11) were separated by partition chromatography. Both IV and V, as well as VI are suitable intermediates for diester synthesis by procedures already applied in the deoxyribonucleotide field.a I n the present work, VI was treated with two molar equivalents of 2’,3‘-di-0-acetyluridine5and dicyclohexylcarbodiimide under the standard condi(2) R. E. Florin, THISJOURNAL, 71, 1867 (1949); 73, 4468 (1951). tions used earlier.3a After work-up, which inDEPARTMENT OF CHEMISTRY C. G. OVERBERGERcluded successive treatments with aqueous acetic OF BROOKLYN POLYTECHNIC INSTITUTE acid to remove triphenylmethyl and tetrahydroN. Y. BROOKLYN, V. G. KAMATH pyranyl groups, and ammonium hydroxide to reRECEIVEDAPRIL14, 1959 move acetyl groups, the desired uridylyl-(5’-. 3’)-uridine (I), Rr 0.19,4 and uridine were found to be the only products and were readily separated. SPECIFIC SYNTHESIS OF THE C6’-Cg‘ INTERRIBONUCLEOTIDE LINKAGE : THE SYNTHESIS OF The synthetic dinucleoside phosphate was characURIDYLYL-(J’ + 3’)-URIDINE’*s terized in a variety of ways; i t was degraded comSir: pletely to uridine-3’ phosphate and uridine by a The problem of the synthesis of ribo-polynucleo- spleen diesterase preparation6 and also by pantides containing the naturally occurring (C5’-C3’) (3) (a) P. T. Gilham and H. G. Khorana, THISJOURNAL, 80, 6212 inter-ribonucleotide linkage is seriously compli- (1958); i b i d . , 81, in press; (b) G. M. Tener, H. G. Khorana, R . cated by the presence of the 2’-hydroxyl group in Markham and E. H. Pol, i b i d . , 80, 6223 (1958); (c) A. F. Turner and ribonucleosides. Consequently, while consider- H. G. Khorana, ; b i d , , in press. Determined in isopropyl alcohol, ammonium hydroxide, water able progress recently has been made in the syn- (7:(4) 1:2).
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COMAIUNICATIONS TO THE EDITOR
1ToI. s1
Acylation of the primary amine grouping in I1 was accomplished with 9-nitrobenzyl chloroformate2 and triethylamine to yield rnethyl-D-a-4carbomethoxy-5,5-dimethyl-a(carbo-p-nitrobenzyloxyamido)-thiazolidineacetate. Saponification of the a-methyl ester grouping with one equivalent of sodium hydroxide and crystallization from acetone-ether yielded ~-~-4-carbomethoxy-5,5-dimethyl- CY- (carbo -9-nitrobenzyloxyamido) - thiazo~ O ~ 138S; lidineacetic acid (111), C ~ V H ~ ~ N m.p. ( 7 ) L. A. Heppel, P. R. Whitfeld a n d K. M a r k h a m , Biochenb. J . , 60, 139’, 02’D 60.9’ (C, 1.17inmethanol). [Found, 8 (1955). MICHAELSMITH C, 47.57; H, 4.08; N, 9.83.1 The infrared spec€3. C. RESEARCH COUKCIL H. G. KHORANA trum (KBr) of this acid was identical to that of the UNIVERSITYOF B. C. \.ANCOUVER 8, B. C., CAXADA corresponding DL-derivative prepared by total RECEIVED APRIL H, 1959 synthesis3 The infrared spectrum of the hydrochloride of 111, m.p. 187-188’, [found, C, 44.39; T H E CHEMICAL CONVERSION O F PENICILLIN G H , 5.25; K, 5.841 wasyidentical to that of the corresponding DL-hydrochloride when measured INTO A BIOLOGICALLY ACTIVE SYNTHETIC PENICILLIN SERIES in dimethyl sulfoxide solution. 1Ye are indebted to Bristol Laboratories of Sir: 11-e wish to report the chemical removal of the Syracuse, K. Y., for financial support and for phenylacetic acid side chain from penicillin G (I) bioassays. to form compound 11, thus opening up a promising (2) 12. 1-1. Carl~enter and D. T. Gish, THIS JOURX.AL, 74, 3818 route for the preparation of synthetic penicillins. 11852). (:i) The I L f o r m of this compound h a s been prepared in this lahoraCompound I1 has been converted into an intermetory h5- , C. Stelakatos using t h e general proccdure of J. C. Sheehan diate (111) in a total synthetic series, thereby com- and P. A. Cruickshank (THISJ O U X N A L , 78, 3683 (19.50)). DL-111 has pleting by relay a transition between a “natural” hem cyclized t o methvl ~ r . - i ~ ~ ~ c a r b o - p - n i t r o h e n z y l ~ x ~ a m i d o l - p r n i c i l l a penicillin and a biologically active synthetic peni- n a t e i n 38% yield. cillin not directly available previously by fermen- DEPARTMEKT JOHN c. SHEEHAX OF CHEMISTRY MASSACHUSETTS INSTITUTE OF TECHXOLOGY tation. JAMES P. FERRIS 39, MASSACHUSETTS Potassiuni benzylpenicillinate (penicillin G , po- CAMBRIDGE RECEIVEDAPRIL 1,1959 tassium salt) was treated with methanol containing a catalytic amount of triethylamine to form potassium a-methyl D-a-benzylpenicilloate, which was T H E CONFIGURATION O F MOLECULAR converted directly in 227, over-all yield by reCOMPLEXES action with methanolic hydrogen chloride to Sir: methyl ~-a-4-carbomethoxy-5,5-dimethyl-a-am~noOrgel and hIullikenl have suggested that molecu2-thiazolidineacetate hydrochloride (II), CloHlSlar complexes may involve a variety of different C1N2O4S,111.p. 174-17.5’ dec., aQ5D 104’ (C, 1.34 in methanol) [found: C, -10.28; H , 6.38; relative orientations of the donor and acceptor. In order to determine the geometrical restrictions N, 9.341. It was established that no change in configura- on charge-transfer interactions in molecular comtion took place during the methanolysis by the plexes, we synthesized and determined the spectra conversion of I1 to the known’ dimethyl D-a-benzyl- of a series of molecules having both the donor and penicilloate [III.~.87-88’> a2jD 82.2’1 in 72% acceptor groups in the same molecule and in a yield with phenylacetyl chloride and triethyl- relatively fixed orientation with respect to each amine. Identity with an authentic sample was other. The donor in each case was the p-aminoestablished by comparison of optical rotation, phenyl system and the acceptor, the ;b-nitrophenyl melting point, mixed melting point and infrared group. The compounds studied were 4-amino-4’nitrodiphenylmethane (I), m.p. 96.9-97.5’ (found spectra (KRr). for C13H1202?uTz:C, 68.55; H, 5.21); 4-amino-4’(11), imp. 136.8-137.5’ (found for nitrobibenzyl c . H ~ C H ~ C O ~ H ~COPK> NH COZCHB C14H1402N2: C, 69.18; H, 5.56); 4-amino-4‘nitro-apdiphenylpropane (111), m.p . 92.0-02.7 ’, 01 C O P C H 11 ~ (found for C15H1802N2:C, 70.52; H, 6.40); cis1-(4-aminophenyl)-%(A - nitrophenyl) - cyclopentane J. (IV), 1n.p. 112.2-113.0° (found for C17H18021i2: p-NOZCsH4CH20CONH C, 72.25; H , 6 6 7 ); and trans-l-(4-aminophenyl)~ H ~ C o 2 c H2-(4-nitrophenyl)-cyclopentane r (V), imp. 76.5-77.3’ C, 72.5Z0;H , 6.53). (found for Cl~HlsOQNz: L/ COzH I1I Compound I involves a 2.52 4. separation for the p-NO2C6H4CHzOCOSH 1-atoms of the ring and a 7.02 A. separation for the - p k O , C H , +atoms. The aromatic rings in I1 and I11 can have an infinite variety of orientations with respect 0 IV to each other because of rotation about the chain (1) H. T. Clarke, J. R. Johnson a n d R . Robinson, editors, “ T h e bonds. In I V the aromatic nuclei are practically creatic ribonuclease. In the latter case, uridine2’,3’ cyclic phosphate was, as expected, an intermediate in the degradation. The synthetic material was, furthermore, chromatographically and electrophoretically identical with a sample of uridylyl(5’4-3’) -uridine prepared enzymically by the general method of Heppel, Vv-hitfeld and Markham.’ Further work on the synthesis of C5’-C3’ linked ribo-oligonucleotides is in progress.
+
+
+
iE-FY
Chemistry of Penicillin,’’ Princeton University Press, Princeton, X e v Jersey, 1949, p tj18.
(1) I, E Orgel and I
