California Lomatiums, Part IV(a): Composition of the Essential Oils of Lomatium rigidum (M.E. Jones) Jepson. Structures of Two New Funebrene Epimers and a Tridecatriene

Journal of Essential Oil Research: JEOR, Nov/Dec 2004 by Beauchamp, Philip S, Descalzo, Josette T, Dev, Barbara C, Dev, Vasu, Et al

Isolation of 2-epi-fi-funebrene I: The GC of the root oil from Sept. 18 collection showed ~24% I. The oil (0.2 g) was first chromatographed over 4 g Si gel using hexane as the mobile phase. The first seven fractions (~3 mL each) were significantly enriched in I, as indicated by TLC and GC. They were combined and further chromatographed over 4 g of 15% AgNO^sub 3^ impregnated silica gel using hexane as the mobile phase. Fractions rich in I were combined to give 11 mg of oil containing -92% I as determined by GC which did not show the presence of II although it was present in the root oil. This sample was used for acquisition of its NMR spectral data (Table II). [α]^sup 24^^sub D^ = 31.5° (c 0.0238 hexane); MS m/z (rel. intensity) 204 [M ] (16), 189(6), 175(4), 161(100), 147(5), 133(32), 120(31), 109(17), 105(22), 93(38), 91(33), 79(20), 77(19), 69(43), 57(12), 55(15), 41(21).

Isomerization of 2-epi-β-funebrene I to 2-epi-α-funebrene II: When the CDCl^sub 3^ solution of I used for NMR data acquisition was left in the refrigerator for a period of about two weeks there was a near complete isomerization to II as determined from its NMR data (Table III). Its GC retention time and MS matched with the RI1385 component in the oil. MS m/z (rel. intensity) 204 [M ] (14), 189(8), 175(1), 161(18), 147(14), 136(7), 133(6), 119(100), 105(29), 93(39), 91(20), 79(8), 77(12), 69(15), 55(6), 41(10).

Preparation of 2-epi-isofunebran-lS ol III: Several fractions, ~60% rich in I obtained during the chromatography of the root oil were combined. The removal of solvent with a rotovap and drying for 5 min at 10 torr gave 80 mg of oil. The oil was subjected to hydroboration-oxidation (6). The crude product was dissolved in 1 mL of 50:50 hexane:ether and filtered through a 1 mL Si gel PrepSep column which was then washed with 8 mL of 50:50 hexane:ether. The filtrate and washings were concentrated with a rotary evaporator to an oily residue. The residue was dissolvedin ImL of 70:30hexane:ether and chromatographed over 3 g Si gel. The column was eluted successively with 5 mL 98:2, 5 mL 95:5, 5 mL 90:10, 10 mL 80:20, 10 mL 70:30, 5 mL 50:40 and 10 mL 50:50 hexane ether. Eighteen fractions, about 2-3 mL each, were collected and every second fraction analyzed by GC and GC/MS. One fraction, 10.3 mg that showed nearly 92% purity and whose MS supported it to be the alcohol III, was selected for NMR data acquisition (Table II). It was then crystallized from hexane and the appropriate crystals m.p. 75-76°C (uncorr.), were chosen for X-ray diffraction work. = [α]^sup 24^^sub D^ 13.9° (c, 0.0208 CH^sub 3^OH); MS m/z (rel. intensity) 222 [M ] (5), 218(9), 204(18), 191(24), 189(25), 179(24), 161(42), 147(20), 135(37), 133(53), 121(35), 119(57), 109(38), 107(63), 105(52), 95(37), 93(72), 91(63), 82(100), 79(51), 69(56), 67(40), 55(34), 41(42).

X-ray analysis of Hl: A colorless fragment of a needle (0.70 × 0.23 × 0.15 mm^sup 3^) was used for the single crystal x-ray diffraction study of C^sup 15^H^sub 26^O. X-ray intensity data were collected at 223(2) K on a Bruker SMART 1000 (7-9) platform-CCD X-ray diffractometer system (Mo-radiation, λ = 0.71073 [Angstrom]). The unit cell parameters were, a = b = 19.5903(18) [Angstrom], c = 7.7487(10) [Angstrom], α = β = γ = 90°, V = 2973.8(5) [Angstrom]^sup 3^, Z = 8, calculated density D^sub c^ = 1.065 g/cm^sup 3^. The space group was 14(1) and direct method was used for structure solution. There was one molecule Of C^sub 15^H^sub 26^O and 0.1875 molecule of hexane present in the asymmetry unit of the unit cell. [Note that the absolute configuration of this chiral molecule can not be determined without any heavy atom.] The -OH group was involved in intramolecular hydrogen bonding. The refinement converged at Rl = 0.0413, wR2 = 0.0946, with intensity, I > 2σ(I).

Tables of positional and thermal parameters are available from the Directory of the Cambridge Crystallographic Data Centre, University Chemical Laboratory, Lensfield Road, Cambridge, CB2 IEW, UK. The request should be accompanied by the full literature citation for this report.