A New ent-Clerodane Diterpene from Hymenaea courbaril var . altissima

Da casca do tronco de Hymenaea courbaril var. altissima (Ducke) foi isolado um novo entclerodano na forma de éster metílico, após esterificação com diazometano, o (-)-(5R,8S,9S,10R)clerod-3-en-15-oato de metila. Foram isolados também dois ent-labdanos conhecidos: o (-)-copalato de metila e (-)-eperuato de metila. Do extrato AcOEt do epicarpo foi isolado, após esterificação com diazometano, o (-)-zanzibarato de metila. As estruturas dos compostos foram elucidadas com base na análise de dados espectroscópicos.


Introduction
Hymenaea is a genus widely distributed from Central to South America and is known popularly as "jatobá", "jataí " or "jutaí ". 1 The wood is used for woodwork and the resin extract is locally used as a remedy for many purposes. 2The chemical composition of the resin obtained from some species of Hymenaea is already known in the literature 3 and recently we reported the isolation of two new ent-clerodane derivatives from the seed pods resin of H. courbaril var.stilbocarpa. 4We now describe the isolation of two known diterpenes (1, 2) and a novel entclerodane (3) from the ethyl acetate extract of H. courbaril var.altissima (Ducke) barks, which grows mainly in a subtropical forest on the Atlantic Coast, 5 and the isolation of a known diterpene (9) from the ethyl acetate extract of its seed pods.Another five compounds (4-8) were also identified by GC/MS analyses.
The full 1 H and 13 C NMR signals assignment was based on homonuclear and heteronuclear 2D experiments (COSY-90, HSQC) and by comparison with the 13 C NMR spectral data of the previously isolated compound 8, 4 which showed a good agreement for the chemical shifts of carbons belonging to the decalin moiety.
The 1 H NMR spectrum also revealed signals for methylene hydrogens (δ 2.13, dd, J 9.0 and 4.4 Hz; 2.35 dd, J 9.0 and 4.4 Hz) adjacent to a carbomethoxyl group and cross peaks in the COSY spectrum showing their coupling to a methinic hydrogen at δ 1.88 (m).This hydrogen was, in turn, connected to the methyl group at δ 0.96 and methylene hydrogens at δ 1.33 (m).The 13 C NMR data connectivity analyses and comparison of 13 C NMR data of the side chain of 3 with those of 2 were in good agreement.The chemical shift of carbon C-19, that appeared at δ 20.6, confirms the trans relationship for A/B ring. 4 The assignments for all signals were fully confirmed by HSQC and HMBC experiments.

Experimental
General 1 H-and 13 C-NMR spectra were recorded in CDCl 3 solution at 300 MHz and 75 MHz, respectively, with a Bruker AC 300/P spectrometer (internal standard TMS).IR spectra of neat samples were obtained on a Perkin-Elmer 1600 series FTIR.Mass spectra of purified compounds were obtained at 70 eV on an Hewlett-Packard 5990/5970 system equipped with a J&W Scientific DB-5 fused silica capillary column (30 m x 0.25 mm x 0.25 mm).Highresolution mass spectra (HRMS) were performed with a VG 7070E spectrometer by electron impact with beam energy of 70 eV.Optical rotations were measured with a Carl Zeiss photoelectric polarimeter.

Isolation
The seed pods and barks of Hymenaea courbaril var.altissima (Ducke) were collected in March 1994 at Fazenda Santa Elisa (IAC-Campinas), São Paulo State, Brazil.A voucher specimen was deposited in the Herbarium of IB-UEC (# no.GS 01/03).Dry barks (360 g) were powdered and extracted with EtOAc (3L) for 5 days at room temperature.After filtration and evaporation of solvent at reduced pressure a crude extract (34 g) was obtained as an oily resin.A sample of resin (789 mg) was esterified with diazomethane and submitted successively for purification using silica gel column chromatography (CHCl 3 : MeOH 1% to 5%, v/v), prep TLC on SiO 2 /AgNO 3 (5%, w/w) eluting with a mixture of different solvents and polarity (petroleum ether/EtOAc/CH 2 Cl 2 ) to yield (-)-methyl copalate

Table 1 .
1H and 13 C NMR spectral data of 3 (300 MHz, 75 MHz) and 13 C NMR spectral data of 2 and 8 in CDCl 3(75 MHz) thank Dr. L.H.B. Baptistella and Dr. C.H. Collins for helpful discussion and suggestions.