Two new prenylflavanones, tanariflavanones A (1), and B (2), and one known compound, (-)-nymphaeol-C (3), were isolated from the fallen leaves of Macaranga tanarius. Compounds 1 and 2 showed inhibition of radical growth of lettuce seedlings at 200 ppm. Their structures were elucidated primarily by NMR, circular dichroism, and mass spectroscopic methods.

Taiwania cryptomerioides HAYATA (Taxodiaceae) is a decay-resistant, endemic tree that grows at elevations from 1800 to 2600 m in the central mountains of Taiwan. It is an economically important tree species in Taiwan. In previous phytochemical investigations, various sesquiterpenes, lignans, diterpenes, and bisflavones were isolated from the heartwood, [1][2][3] bark, 4,5) and leaves [6][7][8][9] of this plant. Recently, we reinvestigated the constituents of the bark of T. cryptomerioides, resulting in the discovery of several new diterpenes with 5(6→7)abeoabietane and podocarpane skeletons. [10][11][12][13][14][15][16][17] In continuing work on the same extracts of the plant, we also obtained five new diterpenoids, designated as 11-hydroxyabieta-8,11,13-trien-7-one (1), 11,12,14-trihydroxyabieta-8,11,13-trien-7-one (2), 6b,7a-diacetoxyroyleanone (3), 7b-hydroxymanoyl oxide (4), and 9a-hydroxyisopimara-8(14),15-dien-7-one (5). In this paper, we describe the isolation and structural elucidation of the above new diterpenes.Compound 1 was isolated as an amorphous solid. The high resolution electron impact mass spectrum (HR-EI-MS) afforded a molecular ion at 300.2080, consistent with the molecular formula C 20 H 28 O 2 and indicated seven degrees of unsaturation. The IR spectrum of 1 showed characteristic absorptions at 3430 (hydroxyl group), 1505, 1625 (aromatic groups), and 1660 (conjugated carbonyl group) cm Ϫ1. The UV absorptions at l max 225 and 267 nm were attributable to the benzoyl moiety. The 1 H-NMR (Table 1) C-NMR signals between 6 and 1, the only difference was a proton attached to C-12 in 1 instead of a hydroxyl group attached to C-12 in 6. Thus, compound 1 was determined as 11-hydroxyabieta-8,11,13-trien-7-one.Compound 2 (Table 2) spectrum showed 20 carbons including a conjugated carbonyl (d C 204.5) and six aromatic carbons (d C 108.8, 118.4, 132.7, 137.3, 151.8, 159.5). From the above characteristics, compound 2 was similar to the structure of 1 with the abieta-8,11,13-trien-7-one skeleton. The only difference was that two meta-phenyl protons in 1 were * To whom correspondence should be addressed. , 11-hydroxyabieta-8,11,13-trien-7-one (1), 11,12,14-trihydroxyabieta-8,11,13-trien-7-one (2), 6b b,7a a-diacetoxyroyleanone (3), 7b b-hydroxymanoyl oxide (4), and 9a a-hydroxyisopimara-8(14),15-dien-7-one (5) were obtained from the bark of Taiwania cryptomerioides. The structures of the new compounds 1-5 were elucidated on the basis of spectral analysis and chemical evidence.