Synthetic studies with Pinus elliottiis rosin derivatives. Oxidation of maleopimaric anhydride methyl ester and trimethyl fumaropimarate

Article

Synthetic studies with Pinus elliottiis´ rosin derivatives. Oxidation of maleopimaric anhydride methyl ester and trimethyl fumaropimarate

Sonia C. Hess^a, Maria I. S. Farah^b, Silvia Y. Eguchib^b, and Paulo M. Imamurac^*

^a Departamento de Morfofisiologia/CCBS, Universidade Federal de Mato Grosso do Sul, CP 549, CEP 79070-900, Campo Grande - MS, Brazil

^bFundação Tropical de Pesquisas e Tecnologia André Tosello, R. Latino Coelho, 1301,CEP 13087-010, Campinas - SP, Brazil

^cInstituto de Química, Universidade Estadual de Campinas, CP 6154, CEP 13083-970, Campinas - SP, Brazil

A ozonólise do éster metílico do anidrido maleopimárico na presença de tetracianoetileno produziu um epóxido e um ozonídeo, e a ozonólise do fumaropimarato de trimetila, seguida por tratamento com Me₂S, forneceu um epóxido, um dieno, um ceto-ácido e um produto de oxidação alílica. Alguns dos compostos obtidos apresentaram atividade antibacteriana contra Staphylococcus aureus, Bacilllus subtilis e Micrococcus luteus.

Ozonolysis of maleopimaric anhydride methyl ester in the presence of tetracyanoethylene led to an epoxide and an ozonide. Ozonolysis of the trimethyl fumaropimarate, followed by treatment with Me₂S, led to an epoxide, a diene, a keto-acid and an allylic oxidation product. Some of the compounds obtained were active against Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus.

Keywords: Pinus elliottiis' rosin, oxidation, maleopimaric anhydride methyl ester, trimethyl fumaropimarate.

Introduction

In the search for biologically active substances, we have envisioned that maleopimaric anhydride methyl ester (1) and fumaropimaric monomethyl ester (2), easily prepared through Diels-Alder reaction of abietane acids present in Pinus elliottiis' rosin¹ with maleic anhydride and fumaric acid, respectively, would be potential starting materials mainly for the synthesis of some C-17 oxygenated naturally occurring polycyclic systems such as 4, 5 and 6^2,3 (Figure 1), if a way could be found to cleave the D¹³ double bond in C-ring. Oxidation of 1 and 2 with KMnO₄^4,5, RuO₄ and O₃^6-8 has been already studied during the establishment of the correct stereochemistry of the Diels-Alder products. As part of our research program on the use of Pinus elliottiis' rosin as chiral synthons⁹, we prepared 1 and 2 in order to cleave the D¹³ double bond using different conditions. In the present paper, we describe the results of our work on the oxidative transformations of 1 and trimethyl fumaropimarate (3), from which two new compounds were isolated and characterized by spectroscopic data. Some products obtained during our investigation were submitted to biological assays and shown to be active against Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus.

Figure 1

Results and Discussion

It is well known that the product of the ozonolysis of olefins depends on the solvent medium, i.e., protic or aprotic¹⁰. Zalkow^6,7 and Halbrook⁸ reported that ozonolysis of 1 and 2 carried out in acetic acid leads to a mixture of many products. Thus we decided to follow the literature suggestion¹¹ to carry out the ozonolysis of 1 at 0^oC in CH₂Cl₂ solution in the presence of tetracyanoethylene (TCNE) in attempt to minimize the formation of the undesired products obtained previously by Zalkow^4,6,7 and Halbrook⁸. Although in this case the mechanism is not clear, the catalytic action of TCNE on the alcoholysis of epoxides is well known due to its p-acid and one-electron acceptor properties¹². Carrying out the reaction under these conditions we isolated, after purification, a known epoxide 7⁷ in 20% yield and the ozonide 8 in 7% yield (Scheme 1). This ozonide proved to be stable at low temperature¹³ and has not been observed before; this is not surprising since there are reports in the literature concerning the isolation of many stable ozonides^14,15. The ozonide was characterized by careful analysis of ¹H and ¹³C NMR data. The hydrogen H-14 appeared at d 3.19 as a singlet and the carbons C-13 and C-14 of ozonide appeared, respectively, at d 112.5 and 106.6. These chemical shifts are in good agreement with those observed for the ozonide of methyl abietate (9) previously prepared in our laboratory⁹.

On the other hand, epoxide 7 was the only product isolated from the ozonolysis of 1, in the absence of tetracyanoethylene (-78^oC; CH₂Cl₂, 20% yield), after treatment with Me₂S. An intractable mixture was obtained when the reaction mixture was treated with NaBH₄ or Zn/HOAc. The reaction of 1 with RuO₄ (25^oC; CH₂Cl₂; NaIO₄/RuCl₃)^16,17 also gave the epoxide 7 in 10% yield and did not cleave the D¹³ double bond to the corresponding keto-acid.

In contrast, ozonolysis of 3 (0^oC; CH₂Cl₂), followed by treatment with Me₂S furnished, as expected, the known diene 10 (10% yield)⁶, epoxide 11⁷ (19% yield), alcohol 12⁶ (18% yield) and the desired keto-acid 13 which was characterized as tetramethyl ester 14 after methylation with diazomethane (32% yield) (Scheme 2). The ¹³C NMR spectrum of 14 showed two new carbonyl carbons [at d 214.6 (C-13, ketone) and at d 171.8 (C-14, ester)]¹⁸. The ¹H NMR spectrum showed four carbomethoxyl groups (at d 3.57; 3.62; 3.64 and 3.66) which was confirmed by ¹³C NMR data (at d 51.7, 51.8 and 51.9 (2x)).

Although Zalkow^4,5 reported the oxidation of 3 with KMnO₄ in basic medium leading to a mixture of products, our protocol was carried out using recent and improved conditions described in the literature: a)¹⁹ KMnO₄ with dibenzo-18-crown-6; CH₂Cl₂; 25^oC; 24 h; b)²⁰ KMnO₄ supported on silica gel; CH₂Cl₂; 25^oC; c)^21,22 KMnO₄ (cat.) with NaIO₄; K₂CO₃; H₂O/t-BuOH; 70^oC; 160 h, in hope to obtain a better yield of 13. Nevertheless, in all cases, the reaction was incomplete and led to an intractable mixture of products.

The desired keto-acid 13 was obtained in only moderate yield and the present result showed that ozonation seems to be the best way to oxidize the hindered D¹³ double bond of 3. The easiest ozonolysis of 3, in comparison with 1, is probably due to the less hindered a-orientation of the carbomethoxyl group at C-24.

The compounds obtained from the oxidation of 1 and 3 were evaluated for antibacterial activity by means of bioautographic tests, following the methodology previously described^23-24 using chloramphenicol as standard. Compounds 1, 2, 12 and 14 proved to be active against gram-positive bacteria (Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus) and were submitted to tests for the determination of the Minimal Inhibitory Concentration (MIC) following the cylinder-cup method²⁵. MIC values are presented in Table 1 and as can be seen, compound 12 was the most active against the gram-positive bacteria. In contrast, Salmonella chokerauesuis, a gram-negative bacteria, was resistant to every substance tested.

Further investigation of the synthesis of some C-17 oxygenated polycyclic systems are underway in our laboratory.

Experimental

All melting points were determined on Kofler block and are uncorrected. TLC was performed on silica gel with fluorescent indicator on glass plates (Silica gel GF₂₅₄, Merck). Column chromatography was carried out on silica gel (Silica gel 60, 0.06-0.2 mm, Merck). NMR spectra were measured on Varian Gemini - 300 and Bruker ACP - 300 (¹H NMR at 300 MHz, ¹³C at 75.6 MHz) instruments, in deuterated chloroform with tetramethylsilane as internal standard. IR spectra were measured on FT IR Perkin-Elmer 16 PC. Optical measurements were run in chloroform, on a polarimeter Carl Zeiss Jena Polamat A. Mass spectra were measured on a high resolution Micromass Autospec (Manchester, UK) spectrometer, using the EI (electron energy 70 eV), source temperature 200^oC and resolution 10,000.

Maleopimaric anhydride methyl ester (1). Pinus elliottiis' rosin was esterified with dimethylsulfate (NaOH, Na₂CO₃/H₂O, Me₂SO₄). After purification by column chromatography with hexane-ethyl acetate mixture (95:5), the mixture of methyl esters was reacted with maleic anhydride according to the literature⁴ to give compound 1 (38 % yield) as a colorless crystals: [a]²⁰_D -31.4 (c 3.0, CHCl₃); mp 211-213^oC; IR (KBr, cm^-1): 2927, 1781, 1720. 1462, 1242, 1222, 1082, 918; ¹H NMR (CDCl₃, d ppm): 5.53 (s, 1H), 3.67 (s, 3H), 3.09 (m, 1H), 3.08 (dd, J = 3; 11 Hz, 1H), 2.71 (d, J = 11 Hz, 1H), 2.51(dt, J = 3; 14Hz, 1H), 2.23 (m, 1H), 1.80-1.35 (m, 11H), 1.30-1.15(m, 2H), 1.15 (s, 3H), 1.00 (d, J = 6,8 Hz, 3H), 0.99 (d, J = 6,8 Hz, 3H), 0.59 (s, 3H); ¹³C NMR: see Table 2; HRMS Calcd. for C₂₅H ₃₄O₅ 414.2406, Found 414.2407 (M⁺).

Trimethyl fumaropimarate (3). Compound 2 was prepared according to the literature procedure²⁶ in 46 % yield. Treatment of 2 with ethereal diazomethane at 0^oC led to product 3 (99 % yield) as a viscous liquid: [a]²⁰_D +27.4 (c 2.5, CHCl₃); IR (KBr, cm^-1): 2951, 1730, 1710, 1435, 1385, 1267, 1199, 1177; ¹H NMR (CDCl₃, d ppm): 5.33 (s, 1H), 3.68 (s, 3H), 3.64 (s, 3H), 3.57 (s, 3H), 2.86 (m, 1H), 2.78 (d, J = 6 Hz, H-22), 2.57 (dd, J = 3; 6 Hz, 1H), 2.38 (m, 1H), 1.10 (s, 3H), 1.80-1.20 (m, 12H), 1.04 (d, J = 7 Hz, 3H), 1.03 (d, J = 7 Hz, 3H), 1.10-0.80 (m, 2H), 0.56 (s, 13H); ¹³C NMR: see Table 2; HRMS Calcd. for C₂₇H ₄₀O₆ 460.2824, Found 460.2822 (M⁺).

Ozonolysis of maleopimaric anhydride methyl ester (1). A rapid stream of ozone containing approximately 3% of O₃ in O₂ was passed through a solution of 1 (250 mg; 0.60mmol) and tetracyanoethylene (102 mg; 0.79 mmol) in 20 cm³ of dichloromethane at 0^oC for 2h until the blue color of excess of ozone was present. The solvent was removed in a rotary evaporator and residue was purified by column chromatography with a hexane-ethyl acetate mixture (7:3 - 1:1) obtaining two products:

Compound 7: (51 mg; 0.12 mmol; 20%) as an amorphous solid: [a]²⁰_D -11.6 (c 3.3 CHCl₃); mp 285-287^oC; IR (KBr, cm^-1): 2923, 1776, 1718, 1467, 1384, 1261, 1231, 1095, 920; ¹H NMR (CDCl₃, d ppm): 3.67 (s, 3H), 3.19 (s, 1H), 2.82 (dd, J = 3; 11 Hz, 1H), 2.80 (m, 1H), 2.64 (dt, J = 3; 14 Hz, 1H), 1.80-1.36 (m, 11H), 1.30-1.18 (m, 2H), 1.24 (m, 1H), 2.43 (d, J = 11 Hz, 1H), 1.95 (m, 1H), 1.18 (s, 3H), 1.04 (d, J = 6.8 Hz, 3H), 0.82 (s, 3H), 0.69 (d, J = 6.8 Hz, 3H); ¹³C NMR: see Table 2; HRMS Calcd. for C₂₅H ₃₄O₆ 430.2355, Found 430.2357 (M⁺);

Compound 8: (20 mg; 0.04 mmol; 7%) as an amorphous solid: [a]²⁰_D -22.4 (c 3.0 CHCl₃); mp 193-195^oC; IR (KBr, cm^-1): 2940, 1776, 1719, 1461, 1255, 1233, 1105, 942; ¹H NMR (CDCl₃, d ppm): 5.62 (s, 1H), 3.67 (s, 3H), 3.07 (t, J = 5 Hz, 1H), 3.03 (dd, J = 4.7; 11 Hz, 1H), 2,75 (d, J = 11 Hz, 1H), 2.50 (dt, J = 3; 14 Hz, 1H), 2.05 (m, 1H), 1.85-1.40 (m, 11H), 1.57 (m, 1H), 1.35-1.20 (m, 2H), 1.18 (s, 3H), 1.05 (s, 3H), 1.04 (d, J = 6.8 Hz, 3H), 0.98 (d, J = 6.8 Hz, 3H); ¹³C NMR: see Table 2; HRMS Calcd. for C₂₅H₃₄O₈ 462.2253, Found 462.2254 (M⁺).

Ozonolysis of trimethyl fumaropimarate (3). A rapid stream of ozone containing approximately 3% of O₃ in O₂ was passed through a solution of 3 (300 mg; 0.65 mmol) in 20 cm³ of CH₂Cl₂ at 0^oC for 2h, until the blue color of excess of ozone was present. Then, oxygen was passed through the solution for removal of excess ozone, dimethyl sulfide (10 drops) was added, and the mixture was stirred 12h at room temperature. After removal the solvent, the residue was purified through column chromatography with hexane-ethyl acetate mixtures (5:5 - 3:7) giving two products:

Compound 10: (29 mg; 0.06 mmol; 10%) as a viscous liquid: [a] ²⁰_D + 50.2 (c 2.0 CHCl₃); IR (KBr, cm^-1): 2949, 1728, 1434, 1387, 1254, 1188, 1172, 737; ¹H NMR (CDCl₃, d ppm): 5.81 (s, 1H), 5.14 (s, 1H), 4.90 (s, 1H), 3.73 (s, 3H), 3.68 (s, 3H), 3.60 (s, 3H), 3.36 (m, 1H), 2.88 (d, J = 6 Hz, 1H), 2.58 (dt, J = 2; 6 Hz, 1H), 1.91 (s, 3H), 1.80-1.30 (m, 14H), 1.20-0.80 (m, 2H), 1.13 (s, 3H), 0.52 (s, 3H); ¹³C NMR: see Table 2; HRMS Calcd. for C₂₇H ₃₈O₆ 458.2668, Found 458.2667 (M⁺);

Compound 11: (59 mg; 0.12 mmol; 19%) as a viscous liquid: [a]²⁰_D -10.3 (c 3.0 CHCl₃); IR (KBr, cm^-1): 2948, 1727, 1434, 1386, 1254, 1195, 1175, 736; ¹H NMR (CDCl₃, d ppm): 3.74 (s, 3H), 3.66 (s, 3H), 3.62 (s, 3H), 3.13 (s, 1H), 3.04 (m, 1H), 2.88 (dt, J= 3; 14Hz, 1H), 2.70 (d, J = 6 Hz, 1H), 2.47 (m, 1H), 1.98 (m, 1H), 1.80-1.10 (m, 13H), 1.17 (s, 3H), 1.09 (d, J = 6.8 Hz, 3H), 0.80 (s, 3H), 0.76 (d, J = 6.8 Hz, 3H); ¹³C NMR: see Table 1; HRMS Calcd. for C₂₇H₄₀O ₇ 476.2774, Found 476.2774 (M⁺);

Compound 12: (50 mg; 0.11 mmol; 18%) as a viscous liquid: [a]²⁰_D +18.3 (c 3.2 CHCl₃); IR (KBr, cm^-1): 3490, 2950, 1724, 1435, 1387, 1254, 1194, 1175, 737; ¹H NMR (CDCl₃, d ppm): 5.62 (s, 1H), 3.71 (s, 3H), 3.67 (s, 3H), 3.60 (s, 3H), 3.15 (brs, 1H), 2.86 (d, J = 6 Hz, 1H), 2.59 (dt, J = 3; 6 Hz, 1H), 1.90-0.90 (m, 15H), 1.39 (s, 6H), 1.13 (s, 3H), 0.58 (s, 3H); ¹³C NMR: see Table 2; HRMS Calcd. for C₂₇H₄₀O₇ 476.2774, Found 476.2775 (M⁺);

Compound 13: (110 mg; 0.21 mmol; 32%). This compound was esterified with ethereal diazomethane at 0^oC to give product 14 (111 mg; 0.21 mmol; 100%) as an amorphous solid: [a]²⁰_D +37.0 (c 2.5 CHCl₃); mp 45-46^oC; IR (KBr, cm^-1): 2959, 1726, 1435, 1240, 1200, 1150; ¹H NMR (CDCl₃, d ppm): 3.73 (s, 3H), 3.65 (s, 3H), 3.63 (s, 3H), 3.57 (s, 3H), 2.94 (dt, J = 4.5; 12Hz, 1H), 2. 80 (m, 1H), 2.41 (d, J = 12 Hz, 1H), 2.30 (d, J = 12 Hz, 1H), 2.05 (q, J = 12 Hz, 1H), 1.95-1.50 (m, 10H), 1.40-1.10 (m, 5H), 1.13 (s, 3H), 1.11 (d, J = 6.8 Hz, 3H), 1.08 (d, J = 6.8 Hz, 3H), 0.73 (s, 3H); ¹³C NMR: see Table 2; HRMS Calcd. for C₂₈H₄₂O₉ 522.2828, Found 522.2826 (M⁺).

Acknowledgements

We thank "Fundação de Amparo à Pesquisa do Estado de São Paulo" (FAPESP) for financial support and Drs. M. Nogueira, A. L. M. Porto, E. G. Magalhães and A. J. Marsaioli for their help and information on bioautographic tests. We also thank Dr. L.H.B. Baptistella for helpful discussion and Dr. F.Y. Fujiwara for reviewing the article.

13. The ozonide could be stored in a freezer without decomposition at -5^oC for few weeks.

18. For convenience, the numbering of carbons for 14 was used the same given for 3.

Received: November 25, 1998

FAPESP helped in meeting the publication costs of this article.

• 1. Seebacher, W.; Hüfner, A.; Haslingeer, E.; Weis, R. Monatsh. Chem. 1995, 129, 697 and references cited therein.
• 2. Ksabati, M. B.; Schimtz, F. J. J. Org. Chem. 1987, 52, 3766.
• 3. Miyamoto, T.; Sakamoto, K.; Arao, K.; Komori, T.; Higuchi, R.; Sasaki, T. Tetrahedron 1996, 52, 8187.
• 4. Zalkow, L. H.; Ford, R. A.; Kutney, J. P. J. Org. Chem. 1962, 27, 3535.
• 5. Zalkow, L. H.; Brannon, D. R. J. Org. Chem. 1964, 29, 1296.
• 6. Zalkow, L. H.; Girotra, N. N. J. Org. Chem. 1963, 28, 2033.
• 7. Zalkow, L. H.; Kulkarni, M. V.; Girotra, N. N. J. Org. Chem. 1965, 30, 1679.
• 8. Halbrook, N. J.; Lawrence, R. V.; Dressler, R. L.; Blackstone, R. C.; Herz, W. J. Org. Chem. 1964, 29, 1017.
• 9. Santos, C.; Rosso, C. R. S.; Imamura, P. M. Synth. Commun. 1999, 29, 1903.
• 10. Bailey, P. S. In Ozonization in Organic Chemistry, Academic Press, New York, vol. I, 1978.
• 11. Herz, W.; Blackstone, R. C. J. Org. Chem. 1969, 34, 1257. See also ref. 10; p.135. 
• 12. Masaki, Y.; Miura, T.; Ochiai, M. Bull. Chem. Soc. Jpn. 1996, 69, 195 and references cited therein.
• 14. Shiojima, K.; Masuda, K.; Ageta, K. Chem. Pharm. Bull. 1990, 38, 79.
• 15. Li, T.; Yang, Y.; Li, Y. J. Chem. Res. (S) 1993, 30.
• 16. Carlsen, P. H. J.; Katsuki, T.; Martin, V. S.; Sharpless, K. B. J. Org. Chem. 1981, 46, 3936.
• 17. Funk, R. L.; Abelman, M. M. J. Org. Chem. 1986, 51, 3247.
• 19. Sam, D. J.; Simmons, H. F. J. Am. Chem. Soc. 1972, 94, 4024.
• 20. Ferreira, J. T. B.; Cruz, W. O.; Vieira, P. C.; Yonashiro, M. J. Org. Chem. 1987, 52, 3698.
• 21. Mitra, R. B.; Muljiani, Z.; Deshmukh, A. R. A. S. Synth. Commun. 1982, 12, 1063.
• 22. Aristoff, P. A.; Johnson, P. D.; Harrison, A. W. J. Am. Chem. Soc. 1985, 107, 7967.
• 23. Homans, A. L.; Fuchs, A. J. Chromatogr. 1970, 75, 327.
• 24. Hamburger, M. O.; Cordell, G. A. J. Nat. Prod. 1987, 50, 19.
• 25. Bruch, M. K. In Methods of Testing Antiseptics: Antimicrobials Used Topically in Humans and Procedures for Hand Scrubs, in Disinfection, Sterilization and Preservation, 4th. Ed., Lea & Febinger, Philadelphia, 1991.
• 26. Halbrook, N. J.; Lawrence, R. V. J. Am. Chem. Soc. 1958, 80, 368.

Publication Dates

• Publication in this collection
  01 June 2000
• Date of issue
  Feb 2000

History

• Received
  25 Nov 1998