Sandoricum koetjape MERR. (syn. Sandoricum indicum CAV.) (Meliaceae) is a medicinal plant widely distributed in tropical areas of Asia. The bark and whole plant have been used as folk medicines as tonic after childbirth and for the treatment of colic and leucorrhea in Malaysia and Indonesia. 1,2) A variety of bioactive triterpenoids including limonoids, polyalcohols, meso-inositol and dimethyl mucate have been isolated from this species previously. [3][4][5][6][7][8] In a previous paper, we described the characterization of koetjapic acid and 3-oxo-olean-12-en-29-oic acid as inhibitors against activation of Epstein-Barr virus early antigen induced by tumor promoter and as ichthyotoxic principles, in the bark of S. koetjape. 9) We have also reported the structures of new modified limonoids, sandrapins A (1), B (2) and C (3) isolated from an EtOAc extract of the leaves of the plant.10) In a continuation of our investigation, further examination of minor terpenoid constituents in the same extract has led to the isolation of additional analogues, sandrapins D (4) and E (5). This paper presents the structures of these new limonoids.The new compounds were isolated by repeated chromatographic fractionation and purification of the EtOAc-soluble portion obtained after removal of lipids from the MeOH extract of the leaves. 12) Thus 4 has the tiglate group in the molecule, which was chemically confirmed by acid hydrolysis yielding tiglic acid. The assignments of the tiglate and acetate groups at C-2, C-3 and C-15 were determined from the HMBC correlations between H-2 (d 5.30) and C-1Ј carbonyl carbon as well as those of H-3 and H-15 with ester carbonyl carbons (169.9, 169.7), respectively ( Table 1). Structure of sandrapin D was thus assigned to the formula 4. Its relative stereostructure was indicated to be the same as that of 1 by analogy of the coupling constants of the methine proton signals (H-1, H-2, H-3, H-11, H-12) on A-and Crings in the 1 H-NMR spectrum, and rotating frame nuclear Overhauser enhancement spectroscopy (ROESY) data.
10)Namely, the trans diaxial relationship between H-2 and H-3 was shown by their large vicinal coupling constant (Jϭ11.5 Hz), and the cis 1,3-diaxial relationship between H-3 and H-5 was implied by their ROE correlation. The ROE correlations among H-5/H-12, H-12/H-17, H-1/H-19, H-1/H-30, and H-30/H-15 as illustrated in Fig. 1 were also characteristic of the stereochemical framework of sandrapins.10)The structure elucidation of sandrapin E (5) was mainly Two new additional trijugin-type limonoids, sandrapins D (4) and E (5), which are analogues of the previously reported sandrapins A-C (1-3), were isolated as minor components from the leaves of Sandoricum koetjape (Meliaceae), and their structures were elucidated on the basis of MS and NMR spectral data.