Xanthones and Coumarins from Kielmeyera lathrophyton

Do extrato hexânico de Kielmeyera lathrophyton foram isoladas duas novas xantonas, 1,5diidroxi-6’-metil-6’-(4-metil-3-pentenil)-pirano(2’,3’:3,2)-xantona, 1,7-diidroxi-6’-metil-6’-(4metil-3-pentenil)-pirano(2’,3’:3,2)-xantona. Uma terceira xantona, a 2,3-metilenodioxixantona, teve a atribuição dos dados de RMN de 13C revista. Foram isoladas ainda seis cumarinas sendo duas delas inéditas, 7-hidroxi-8-(3-metil-1-oxobutil)-4s butil-6’,6’-dimetilpirano(2’,3’:5,6)cumarina e 7-hidroxi-8-(2-metil-1-oxobutil)-4s-butil-6’,6’dimetilpirano(2’,3’:5,6)-cumarina. Além dessas substâncias foram isolados ainda o δ-tocotrienol, a friedelina, o 24 α-etilcolest-5-en-3-ona e o 24α-etilcolest-5,22-dien-3-ol. Estes compostos foram identificados através de suas propriedades espectroscópicas e por comparação de seus dados espectroscópicos com dados da literatura.

In the species K. lathrophyton, which was harvested on a "campo rupestre" area in the Chapada Diamantina, Bahia state, a region localized between the coast and the Central plateau, we found beyond xanthones 4-alkyl and 4-phenyl coumarins.

Plant material
Kielmeyera lathrophyton, Saady, was collected at Parque Nacional da Chapada Diamantina, Bahia, Brazil, in August 1996.A voucher specimen, N o 35942, has been deposited in the Alexandre Leal Costa Herbarium, Instituto de Biologia, Universidade Federal da Bahia, Salvador, Brazil.
The 1 H-1 H COSY and the long range correlations showed by the 1 H- 13 C COSY (J 9 Hz) (Table 2) confirmed the assignments for compound 3.The correlations between the signal at δ 7.64 (H-1) with signals at δ 153.6 (C-3) and 153.7 (C-4a) and those of the signal at δ 6.89 (H-4) with signals at δ 116.6 (C-9a) and 145.3 (C-2) substantiate the proposed structure.
Both compounds 4 and 5 have molecular formula C 23 H 28 O 5 , deduced by EIMS (M + = 384) and 13 C NMR. Spectral data suggested for both 4 and 5 the 4-alkylcoumarin skeleton with a chelated hydroxyl 14,15 .They showed very similar 1 H and 13 C NMR data and structurally differ only in the C-8 acyl side chain.The 1 H NMR spectra (Table 3) of these compounds showed signals for the 6',6'-dimethylchromene ring, a H-3 singlet, one hydrogen of chelated hydroxyl, one acyl side chain and a 4-s-butyl group.
The locations of the substituents around the aromatic coumarin ring are supported by long range correlations (Table 4) and nOe experiments.The long range correlations of the signal at δ 6.13 (H-3) with the resonances at δ 102.8 and 159.6 permitted assignment of these signals to C-4a and C-2, respectively.In accordance with the accepted neoflavonoid oxidation pattern 14,20 , carbons C-5 and C-7 of the aromatic ring are oxygenated, thus the correlations of the hydrogen at δ 14.49 with the resonances at δ 104.7 (C-8), 106.2 (C-6), and 162.9 (C-7) and the correlation of the signal at δ 6.74 (H-4') with the signal at δ 157.3 (C-5) allowed location of the OH at C-7 and the 6',6'-dimethylchromene ring at C-5 and C-6.Consequently the 3-methyl-1-oxobutyl group was placed at C-8.By exclusion, the s-butyl group was located at C-4.This assumption was corroborated by the enhancement of the signal at δ 1.24 (H-1''') in the NOEDIF experiment when H-3 (δ 6.13) was irradiated.
*These signals may be interchanged; values in parentheses indicate coupling constants.