April 20, 1962
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1511
rearrangement of the phenylalanine side chain. hybridized carbon atoms axe fixed in a completely A close biochemical analogy is the recently dis- cisoid configuration and each presumably is incovered methylmalonyl-coenzyme A succinyl- volved directly in bonding to the metal atom. It is of interest then to determine whether linear coenzyme A isomerization.13 A less likely explanation of our results would unsaturated carbonium ions can act as ligands in involve a carboxylation reaction utilizing carbon similar complexes; such carbonium ions possess the dioxide produced by decarboxylation of the required vacant, low energy molecular orbitals but, phenylalanine-l-C14. If this were the case one in contrast to the cyclic systems above, in certain would expect a much more general labeling of the trans configurations not all of the unsaturated alkaloids by the radioactive carbon dioxide. This carbon atoms can be simultaneously bonded to expectation was realized in subsequent tracer ex- the metal. This may be the reason then why we periments. Sodium bicarbonate-C1* (24.8 mg., have been unable to prepare the trans-penta1.0 me.) was fed to Datura plants as previously dienyl-ion tricarbonyl cation (I) by direct hydride described and two weeks later radioactive hyoscy- abstraction from trans - 1,3 - pentadiene - iron triamine (5.5 X lo5 d.p.m./mM.) and hyoscine (4.2 carbonyl using triphenylmethyl perchlorate. This x 106 d.p.m./mM.) were isolated, representing reaction proceeds readily for the cyclic diene coma 0.008yGincorporation of tracer into the alkaloids. p l e ~ e s . ~Salts of two of the complexed linear Hydrolysis of the hyoscyamine yielded tropine (2.4 X lo5 d.p.m./mM.) and tropic acid (3.1 X CHs. l o 6 d.p.m./mM.). Systematic degradation of the tropic acid as previously described indicated that it was non-specifically labeled, the percentage activity a t C1, Cf, CS, and on the aromatic carbons being 16,4, 16, and 65yG,respectively. I I1 We could speculate on the mechanism of the rearrangement of the phenylalanine side chain. However, we feel that scientific journals are currently being filled with far too many incontinent biogenetic hypotheses, and we will withhold our ideas until the completion of additional experimental work. (13) C f . R . Stjernholm and H. G. Wood, PYOC.N a f l . Acad. Sci., 47, 303 (1961), and ref. cited-therein.
I11 IV SCHOOL OF CHEMISTRY MARYL. LOUDEN UNIVERSITY OF MINNESOTA EDWARD LEETE carbonium ions have, however, been obtained fram the corresponding alcohols. trans-trans-2,414, MINNESOTA MINNEAPOLIS Hexadien-1-01 and Fe(C0)6 reacted to form transRECEIVED FEBRUARY 15, 1962
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trans 2,4 - hexadien - 1 - 01 - iron tricarbonyl (II).s (Anal. Calcd. for CgH1004Fe: C, 45.41; PENTADIENYL AND HEXADIENYL CARBONIUM IONS H, 4.23. Found: C, 45.67; H, 4.15.) Treatment AS LIGANDS IN STABLE COMPLEX CATIONS of this alcohol with HClO4 in acetic anhydride Sir : afforded a yellow crystalline precipitate of hexaRecently several cyclic unsaturated carbonium dienylium-iron tricarbonyl perchlorate in almost ions, e.g., the tropylium, cyclopentadienyl,* cyclo- quantitative yield. (Anal. Calcd. for CgHg0,h e ~ a d i e n y l ,cycloheptadienyl,4 ~ and cyclooctatri- ClFe: C, 33.73; H, 2.83; C1, 11.07. Found: C, enyls cations, have been found to bond with certain 33.49; H, 2.87; C1, 10.89.) The structure (111) metal carbonyl groups in the formation of remark- is assigned to this cation for several reasons. The ably stable organo-metallic cations. Two major salt reacted with NaBH4 to produce hexadienefactors concerning the stability of these complex iron tricarbonyl. Reaction of (111) with water cations appear to be the donor properties of the n gave a complex alcohol (IV), isomeric with (11). electrons and the "back donation" of electrons from (Anal. Calcd. for C9HIo04Fe: C, 45.41; H , 4.23. the metal atom to the organic ligand through inter- Found: C, 45.40; H, 4.57.) This new alcohol action of filled d orbitals of the metal with vacant T also generated the perchlorate of salt I11 when molecular orbitals of the carbonium ion ligand. liberated with HCIO,. Decomposition of (IV) This latter interaction is particularly important with FeC& in alcoholic sodium acetate solution for, a t the same time, i t increases the metal- liberated a hexadienol which, on catalytic hydroligand bonding, decreases the electron density genation, absorbed 1.9 mole of hydrogen to give on the metal, and decreases the electrophilicity 2-hexanol. Compound (IV) must therefore be of the carbonium ion moiety. I n each of the 1,3-hexadien-5-ol-iron tricarbonyl. Now since only cyclic carbonium ions mentioned above, the sp2 dienes in the cisoid configuration produce stable diene-iron tricarbonyl complexes, carbon atoms (1) H. J. Dauben and L. R. Honnen, J . A m . C h s p . Soc., 80, 5570 1 and 4 must now be cis with respect to the C2-G (1958). (2) A. Davison, M. L. H. Green and G. Wilkinson. J . Chsm. Soc., bond in (IV). Although it has not yet been 3172 (1961). definitely proven it would seem most likely t h a t (3) E. 0. Fischer and R . D Fischer, Anerw. Chsm., 71.919 (1960). the geometrical inversion has taken place during (4) H. J. Dauben and D. 5. Bertelli, 1.A m . Chcm. Soc., 83, 497 (1961). (5) G.W. Schraueer, J . Am. Chmm. Soc., 83, 2986 (lQ61).
(6) Decomposition of this complex by treatment with FeCh in alcoholic sodium acetate regenerated the starting alcohol.
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Vol. 84
reaction of (11) with HC104, the driving force resulting from the increased bonding between the carbonium ion and the metal. Reaction of trans-1,3-pentadien-5-01with Fe(CO), gave trans-l,3-pentadien-5-ol-iron tricarbonyl (v). (Anal. Calcd. for C8H8O4Fe: c, 42.89; H, 3.59. Found: C, 43.29; H, 3.25.) Treatment of this with HClO, produced pentadienylium-iron tricarbonyl perchlorate (VI). ( A m l . Calcd. for CsH707ClFe: C, 31.35; H , 2.30; C1, '11.57. Found: C, 31.48; H, 2.40; C1, 12.09.) By analogy with the previous salt this cation is assigned the all-cis structure isomeric with I. The two new cations reported here are remarkably stable as is evident from the fact that both alcohols (11) and (V) react with triphenylmethyl perchlorate to produce quantitative yields of triphenylmethanol and the perchlorate of salts 111 and VI, respectively. We thank the Robert A. Welch Foundation and the Alfred P. Sloan Foundation for financial assistance.
3i.84; H, 8.54; OCH3, 9.31; C-CHa, 13.45; neut. equiv., 334; pK'a (water), 4.51. The n.m.r. spectrum5 of I in deuteriochloroform indicates the presence of three C-methyl groups each a to one hydrogen [doublets centering a t 6 = 0.94 (3 hydrogens) and a t 6 = 1.2 (6 hydrogens), J's = 6 cps.], one methyl ketone (singlet, 6 = 2.1), one methoxyl group (singlet, 6 = 3.4), and a total of 28 hydrogens (signal area integration based on two exchanging hydrogens centering a t 6 = 6.9). Reduction of I with sodium borohydride gave an oil which exhibited absorption in the infrared a t 5.81 p and no y-lactone band, thus indicating that in I the carbonyl group is not y to the carboxyl group. Acid hydrolysis of I yielded chalcose and an acidic aglycone I1 (5.75 p ) . The sodium salt of I1 showed no absorption in the carbonyl region (5.5-6.0 p ) , suggesting hemiketal formation involving the methyl ketone and the hydroxyl group generated by acid hydrolysis. Oxidation of I with sodium hypoiodite gave iodoform and acid I11 (5.84 p ) . Acid hydrolysis of I11 yielded chalcose and a y-lactonic acid IV (5.64, 5.83 p ) . DEPARTMENT OF CHEMISTRY UNIVERSITY OF TEXAS J. E. MAHLER These data indicate that chalcose is y to the methyl AUSTIN,TEXAS R. PETTIT ketone group, as in I, but not y to the carboxyl group. RECEIVED MARCH9, 1965 Esterification of the y-lactonic acid IV with methyl iodide-silver oxide gave the lactonic A DEGRADATION PRODUCT OF CHALCOMYCIN : methyl ester V (5.61, 5.74 p ) . Treatment of V 2,4-DIMETHYL-3-CHALCOSYLOXY-6with sodium methoxide in methanol yielded, OXOHEPTANOIC ACID through elimination, the a,@-unsaturatedester VI, Sir : which shows the expected ultraviolet absorption 216 mp, E 1.2 X lo3) and infrared specPrevious communications have shown that the antibiotic chalcomycin' contains two new sugars, trum (5.78, 5.85, 6.04 p ; no OH band a t 3 p ) . chalcose2 and m y c i n o ~ e . ~We now wish to report VI was ozonized and then hydrolyzed to give the structural elucidation of a CIS acid (I, 2,4- pyruvic acid and a-methylsuccinic acid, both dimethyl - 3 - chalcosyloxy - 6 - oxoheptanoic acid) identified by paper chromatography and infrared which has been obtained as a degradation product spectroscopy. The above data are thus consistent with structure I and eliminate alternative strucof chalcomycin. tures having the methyl ketone y to the carboxyl 0 CH3 CH3 0 POUP. I I I1 II Compound I was simultaneously 0-methylated CHs- C-CHZ-CH-CHCH-COH and esterified by treatment with methyl iodide and I silver oxide to give VII, which then was oxidized with trifluoroperacetic acid6 to give acetate VI11 ; the latter was reduced with lithium aluminum I hydride to give dialcohol IX. Methanolysis of I X yielded the oily methyl-2-0-methylchalcoside CHOCH, I and triol m.p., 52.5-54', [CrIz3D +1l0 (c 1.5%, CH? methanol) [Anal. Calcd. for C1H1603: C, 56.73; $H IH, 10.88. Found: C, 56.55; H, 11.241. X reacted with acetic anhydride in pyridine a t room CHJ temperature to give a triacetate [Anal. Calcd. I for C13H2206:C, 56.92; H, 8.08; acetyl (3), Oxidation of chalcomycin with periodate-per- 47.08. Found: C, 57.09; H, 8.00; acetyl, 48.091. manganate4 gave I, m.p. 103-104°, infrared (C- The n.m.r. spectrum of X5 in deuterium oxide D (c 1.670,water) [.jnal. shows five hydrogens CY to oxygens (6 = 3.8 to HC13) 5.83 p, [ ( Y ] ~ ~-23" to oxygen (6 = 2.0 Calcd. for C16H2807 (332.38): C, 57.81; H, 8.49; 4.4), two hydrogens not OCH3 (l), 9.34; C-CH3 (4), 18.09. Found: C, to 2.6), two secondary methyl groups or one isopropyl group (two sets of doublets centering a t (1) Parke, Davis & Company, Belgian Patent 587,213,August 2, 6 = 1.33 and 6 = 1.36, J ' s = 7 cps.), but no 1960. primary or tertiary methyl groups. The analytical (2) (a) P. W.K. Woo, H. W. Dion and Q. R. Bartz, J . A m . Chem. Soc., 83, 3352 (1961); (b) P.W.K . Woo, H. W. Dion and L. F. Johnand n.m.r. data establish the structure of X as either
-
P
ET1
x,
~
i
(Y
son, ibid., 84,1066 (1962). (3) H. W. D i m , P. W. K. Woo and Q . R. Bartz, i b i d . , 84, 880
(1962). (4) R. (1955).
U. Lemieux a n d E , von Rudloff, Can. J . Chcm., 3 8 , 1701
(5) Obtained a t 60 M c . ; chemical shifts are given in p . p m relative t o tetramethylsilane as 0. (6) W. D. Emmons and G. B. Lucas, J . A m . Chem. Sac., 11, 2287
(1955).
