Structures of new lignans from larix leptolepis gord.

Two lignans constructed from tri-phenylpropanes, leptolepisol A and B, both of which have w-hydroxypropane as a side chain were isolated from inner bark of Larix leptolepis Gord. Leptolepisol A is optically active ([%]i7-3.1, c=O.97 in methanol), and shows following spectral properites: Wil max, EtoH (run) 281(E6676); IRv if: (cm-1 ) 3400, 1605, 1510, 1380, 1270, 1140, 1025; MS m/e 538, 360, 342, 330, 327, 180, 137; 'H-NMR (100 MHz)b(;;s)2Co+D20 (ppm) 1.94 (2H, m, H$'), 2.64 (2H, t, J=8.0Hz, Ha?'), 3.58 (2H, t, J=6.5Hz, Ha"), 3.82 (6H, s, OCH31, 3.86 (3H, s, CCH31, 3.2-4.0 (5H, m, Hy, HB', H~J/), 4.42 (lH, m, HA), 4.92 (lH, d, J=6.0Hz, Ha), 5.58 (lH, d, J=6.0Hz, Hcx'), 6.6-7.2 (8H, m, Ar-H). The results are similar to those of monomethyl ether of 2,3-dihydro-7-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-3-hydroxymethyl-5-benzofuranpropanol (III) which was isolated by Popoff and Theander 1) from pine tree as glycoside, and later by us from inner bark of Larix leptolepis, too. 2) In general, a compound having benzyl hydroxyl group like I shows no parent peak but a peak of dehydrated one (M+-H20). 3) The peak at m/e 360 corresponds to dihydrodehydrodiconiferyl alcohol, and that at m/e 180 shows the existence of coniferyl alcohol fragment. Exhaustive methylation of leptolepisol A with dimethyl sulfoxide/ NaH and CH3I (procedure of Hakomori) gave pentamethyl ether Ia which shows a parent peak at m/e 626.3101 (Calcd. for C35H46010: 626.3091). Other abundant ions are at m/e 356(W), 238(V), 207(W), 181, and 151. Acetylation of A with acetic anhydride-pyridine gave pentaacetate Ib, M+ m/e 766. 1 H-NMR of Ib reveals the presence of four alcoholic acetoxyl (2.30 ppm) . The acetoxyls (2.02, 2.05, 2.07 ppm) and one phenolic NMR signal at 4.62 ppm (HP) was proved to couple with