Further Aporphine Alkaloids from Phoebe lanceolata

Stem bark of Phoebe lanceolata was extracted with ethanol and fractionated with ethyl acetate yielded soluble and insoluble fractions. Ethyl acetate insoluble fraction was subjected to column chromatography afforded two oxalyl-fused didehydroaporphine alkaloids, N-6/C-7 oxalyl-fused 2,9-dihydroxy-1,10-dimethoxy 6a,7-didehydroaporphine and N-6/C-7 oxalyl-fused 1,2,9,10-tetramethoxy 6a,7-didehydroaporphine along with well known β-sitosterol and β-sitosterol glucoside. The structures of isolated compounds were elucidated by chemical and spectral analysis.


Introduction
Phoebe lanceolata belonging to family Lauraceae is an evergreen tree and well reputed in traditional medicine in India [1].Ethanolic extract of the stem bark showed antidiabetic, antibacterial and antifungal activity (preliminary work done by us at different laboratory).We recently reported an aporphine alkaloid, nordelporphine [2] from this source and now outlined the isolation and characterization of two oxalyl-fused didehydroaporphine alkaloids.

Results and discussion
Compound 1 was isolated as black crystals, m.p. 280-283 0 C (uncorr.) deduced the molecular formula C 20 H 15 NO 6 from the molecular ion at m/z 365.7 in the LC-EIMS (positive mode).This compound was elucidated as N-6/C-7 oxalyl-fused 2,9-dihydroxy-1,10-dimethoxy 6a,7didehydroaporphine by direct comparison (UV, IR and NMR) to published data for laurodionine [3] isolated from P. formosana.Compound 2 was isolated as black-brown crystals, m.p. 205 0 C deduced the molecular formula C 22 H 19 O 6 N from the molecular ion at m/z 393.3 in the EIMS.The IR absorptions at υ KBr max 1734 cm -1 was characteristic for carbonyl function. 1H NMR spectrum revealed the presence of four methoxy (δ 3.92, 3.63, 3.76 and 3.85) and three aromatic protons (δ 7.81, 7.12 and 6.73). 13C NMR spectrum expressed the evidence for two carbonyl groups (δ 163.83 and 173.33).DEPT (135 0 ) showed the presence of four CH 3 , two CH 2 , three CH and thirteen quaternary carbons.HMBC and NOESY correlations are shown in Fig. 2.These data were somewhat similar to that of 1 except the presence of two methoxy groups instead hydroxy groups.On methylation [4], compound 1 afforded black brown product identical to 2 indicated that the locations of methoxy groups in 2 were similar to those of hydroxy groups in 1.The HMBC correlation of OCH On the basis of these findings and the proposed structure described by Castedo et al., [5], the compound 2 was characterized as N-6/C-7 oxalyl-fused 1,2,9,10-tetramethoxy 6a,7-didehydroaporphine.

General
Melting points were determined on Perfit melting point apparatus; UV spectra on Perkin-Elmer, Lambda-25 spectrophotometer in MeOH; IR spectra on Perkin-Elmer, Spectrum RX I FT-IR spectrophotometer (KBr discs); NMR spectra on JEOL NMR spectrophotometer (300 MHz for 1 H and 125 MHz for 13 C in DMSO, TMS as internal standard); LC-EIMS on Finnigan MAT spectrophotometer.Preparative TLC (0.5 mm thick layer) was carried out on silica gel (Merck 10-40 μ) spots were detected using UV at 254 and 365 nm and Dragendorff's reagent.

Plant material
Stem bark (6 kg) of P. lanceolata was collected from Kartikswami temple, Dist.Chamoli (Uttarakhand) and identified by Prof. R.D. Gaur, Department of Botany, H.N.B. Garhwal University Srinagar.A voucher specimen (GUH-17598) of the plant was deposited in the Departmental Herbarium.

Methylation of compound 1
Dimethyl sulfate (1.5 mg) and dry potassium carbonate (1.5 mg) were added to compound 1 (5 mg) in 5 ml of acetone.The mixture was stirred vigorously and refluxed for 30 minutes in round bottom
position of all methoxy groups.EIMS (positive mode) revealed a molecular ion at m/z 393, another ion at m/z 377 (loss of CH 4 ) and the most abundant ion [C 16 H 5 NO 4 ] •+ at m/z 275 was due to loss of C 5 H 10 O 2 .