126 J. Org. Chem., Vol. 42, No. 1, 1977
Gender and Marshall
Structure Determination of Cyclopropane-Substituted Acids by Mass Spectrometry Walter J. Gender* and John P. Marshall Deptrrtment of Chemistry, Boston University, Charles River Campus, Boston, Massachusetts 02215 Received April 7, 1976
Calibration information has been obtained that will be useful in mass spectral studies of bis cyclopropane meromycolic compounds derived from mycobacterial mycolic acids. The compounds examined include a synthetic meromycolic ester, its monoketo derivatives, and its pyrrolidide. Methyl cis-9,lO-methyleneoctadecanoateand its derivat,ives were also examined. The study shows that the monoketo compounds are to be preferred. The mycolic acids, isolated from tuberculosis bacteria, are high molecular weight P-hydroxycarboxylic acids carrying a tetracosanyl (or docosanyl) group on the CY position.'P2 In the many inquiries into the nature of these compounds, pyrolysis of the methyl esters 1 to the corresponding meromycolaldehydes (2) plus methyl hexacosanoate (3) has been a stanOH
I
K-CH-CH-COOCH,
I
C'JL (methyl mycolate) 1
1
heat
i
+
R--CH=O
Cj4H4&H2COOCH,
(meromycolaldehyde)
(methyl hexacosanoate)
2
3
I
YH
XO~: mol wt, 310. Found: mle 310 (injection port 180 "C). Cyclopropyl Ketones 7 and 8 from Methyl cis-9,lO-Methyleneoctadecanoate (6). An oxidation mixture was made up by dissolving 0.41 g of chromium trioxide in 3.3 ml of 1:l acetic anhydrideacetic acid and diluting with 23.5 ml of carbon tetrachloride. Methyl cis-9,lO-methyleneoctadecanoate (10 mg) in 0.2 ml of carbon tetrachloride on treatment with 0.84 ml of the oxidation mixture a t 0 "C for 2 h furnished the keto products which were separated by preparative layer chromatography. Analytical thin layer chromatography showed single spots with R f 0.25 for the 8-keto compound 7 and 0.30 for the 11-keto compound 8.8 Calcd for CZnH3603: mol wt, 324. Found for both compounds: rnle 324. Pyrrolidide 9 of cis-9,10-MethyleneoctadecanoicAcid. Essentially by following earlier direction^,'^,^^ 10 mg of methyl cis9,lO-methyleneoctadecanate with pyrrolidine and acetic acid furnished pyrrolidide 9 (10 mg) as a faintly yellow oil.
J . Org. Chem., Vol. 42, No. I , 1977 129 Calcd for C Z ~ H ~ ~ mol N Owt, : 349. Found: rnle 349. Monoketo Derivatives (10-13) of Synthetic Methyl Meromycolate (5). The bis cyclopropane methyl meromycolate (2.0 mg) in 0.18 ml of carbon tetrachloride was allowed to stand for 1h with 0.08 ml of the oxidation mixture. Another 0.05-ml portion was then added, followed after 1.5 h by a third portion. After a total reaction period of 4.5 h, the oxidation mixture was processed as before. Preparative-plate chromatography (silica, benzene solvent) afforded the desired mixture of monoketo esters (10-13) as a white solid showing a single spot on analytical thin layer chromatography ( R f 0.55 with benzene on silica). Pyrrolidide 14 of Synthetic Meromycolic Acid (5). By employing directions essentially the same as these used for methyleneoctadecanoic compound 9,1.2 mg of the bis cyclopropane methyl meromycolate ( 5 ) was warmed with 0.5 ml of pyrrolidine plus 0.05 ml of glacial acetic acid. The crude product was purified on a preparative-layer plate (ether-benzene, 2:3), to give the white solid pyrrolidide 14.
Calcd for CBOHIISNO: mol wt, 865. Found: m/e 865, with only traces of peaks a t mle greater than 865.
Acknowledgment. This investigation has been supported by US.Public Health Service Grant 09308 from the National Institute of Allergy and Infectious Diseases. Registry No.-5, 59014-67-4; 6, 3971-54-8; 9, 60103-87-9; 10, 60103-88-0; 1 1, 60103-89-1; 12, 60103-90-4; 13, 60103-91-5; 14, 60103-92-6; methyl oleate, 112-62-9. Supplementary Material Available. The full mass spectral line diagrams for all compounds discussed in this paper (8 pages). Ordering information is given on any current masthead page.
References and Notes (1) J. Asselineau, "The Bacterial Lipids", Holden-Day, San Francisco, Calif., 1966; N. Polgar in "Topics in Lipid Chemistry", Vol. 2, p 234, F. D. Gunstone, Ed., Wiley, New York, N.Y., 1971, p 234. (2) (a) M. B. Goren, Bacteriol. Rev., 36, 33 (1972); (b) Tubercle, 56, 65 (1975). (3) For example, see W. W. Christie in "Topics in Lipid Chemistry", Vol. 1, F. D. Gunstone, Ed., Logos Press, London, 1970, p 19. (4) W. J. Gensler, J. P. Marshall, J. J. Langone, and J. C. Chen, J. Org. Chem., accepted for publication. (5) D. E. Minnikin and N. Polgar, Tetrahedron Lett., 2643 (1966). (6) H. Weitkamp, U. Hasserodt, and F. Korte, Chem. Ber., 95, 2280 (1962). (7) J. A. McCloskey in "Topics in Lipid Chemistry", Vol. 1, F. D. Gunstone, Ed., Wiley-lnterscience, New York, N.Y., 1970, p 409. (8) J.-C. Prome, Bull. Soc. Chim. Fr., 655 (1968). (9) R. Wood and R . Reiser. J. Am. Oil Chem. Soc., 42, 315 (1965). (10) W. W. Christie and R. T. Holman, Lipids, 1, 176 (1966). (1 1) J. A. McCloskey and J. H. Law, Lipids, 2, 225 (1967). (12) J. A. McCloskey,J. W. Polacheck, 8.E. TroDD, . . and J. H. Law, J. Biol. Chem.. 241, 3362 (1966). (13) H. Budzikiewicz, C. Djerassi, and D. H. Williams state ("MassSpectrometry of Organic Compounds", Holden-Day, San Francisco, Calif., 1967, p 183) that there is some tendency to find preferred cleavage at the point of attachment of alkyl groups to a cyclopropane ring. This generalization appears not to be well founded. (14) D. E. Minnikin and N. Polgar, Chem. Commun., 312 (1967). (15) J.-C. Prome and C. Asselineau, Bull. SOC.Chim. f r . , 21 14 (1966). (16) R. A. Andersson, W. H. Heimermann, and R. T. Holman, Lipids, 9, 443 (1974). (17) See also G. Hugel, L. Lcds, J. M. Mellor, and G. Ourisson, Bull. SOC.Chim. Fr., 2894 (1965). (18) Cf. K. Biemann, "Mass Spectrometry',McGraw-Hill, New York, N.Y., 1962, p 101; F. W. McLafferty, "Interpretation of Mass Spectra", 2d ed,W. A. Benjamin, Reading, Mass., 1973, p 123. (19) W. Vetter, W. Walther. and M. Vecchi, Helv. Chim. Acta, $4, 1599 (1971). ( 2 0 ) B. A. Andersson and R. T. Holman, Lipids, 9, 185 (1974). (21) B. A. Andersson. W. W. Christie, and R. T. Holman, Lipids, 10, 215 (1975). (22) But note that, in a different run with the same pyrrolidide 14, the m/e 626 peak was appreciably more abundant (55% on a comparable scale). (23) J. H. Beynon, "Mass Spectrometry and Its Applications to Organic Chemistry', American Elsevier. New York, N.Y., 1960, p 296. (24) W. W. Christie, F. D. Gunstone, I. A. Ismail, and L. Wade, Chem. phys. Lipids, 2, 196 (1968).
