OXYGEN-CONTAINING BICYCLIC MONOTERPENES - H-1, C-13, AND O-17 NMR SPECTROSCOPIC AND X-RAY-DIFFRACTION STUDIES OF 7 OXIDATION-PRODUCTS OF (-3-CARENE())

Seven oxidation products of 1S,6R)-(+)-3,7,7-trimethylbicyclo[4.1.0]he pt-3-ene [naturally abundant terpene, (+)-3-carene)] 1; S,6R)-3,7,7-tr imethylbicyclo[4.1.0]hept-3-en-2-one (3-caren-2-one) 2, S,6R)-3,7,7-tr imethylbicyclo[4.1.0]hept-3-en-5-one (3-caren-5-one) 3, -3,7,7-trimeth ylbicyclo[4.1.0]hept-3-ene-2,5-dione (3-carene-2,5-dione) 4, 3S,4R,6R) -(+)-3,7,7-trimethylbicyclo[4.1.0]heptene 3,4-trans-oxide (trans-3,4-e poxy-3-carene) 5, 7-trimethylbicyclo[4.1.0]heptane-3-exo-4-endo-diol ( carane-3-exo-4-endo-diol) 6 and ydroxy-1-methylethyl)bicyclo[3.1.0]hex an-2-endo-ol 7 and 6R)-3-endo-7,7-trimethylbicyclo[4.1.0]heptan-4-one (trans-4-caranone) 8 have been obtained by oxidation with tert-butylch romate, selenium dioxide, hydrogen peroxide and peracetic acid. The H- 1, C-13 and O-17 NMR spectra of the purified oxidation products have b een recorded and assigned. In addition to C,H-COSY spectra, the 1J(C,H ) coupling constants were especially useful in C-13 NMR spectral assig nment. The differentiation between isomeric ketones 2 and 3 is based o n a clear difference in the C-13 NMR shifts of the double bond methyl. The stereochemical structure elucidation of oxide 5 is based on lanth anide shift reagent [Eu(dpm)3] induced effects. For ketone 8, molecula r mechanics (MM) calculations and comparison of experimental and theor etical 3J(H,H) coupling constants are needed for a final structure elu cidation. The assignment of O-17 NMR lines of diols 6 and 7 is based o n literature values. The crystal structures and absolute configuration s of pure enantiomers of diols 6 and 7 have been determined by X-ray d iffraction. Crystal data: a = 7.659(2), b = 10.804(3), c = 25.509(4) a ngstrom, orthorhombic, space group C222(1), Z = 8 (6) and a = 8.076(4) , b = 8.836(2), c = 12.487(3) angstrom, orthorhombic, space group P2(1 )2(1)2(1), Z = 4 (7).