Akira Sakakibara

Lignans of Larix leptolepis

Abstract Five lignans have been isolated from wood of Larix leptolepis . They are identified as 1-(4-hydroxy-3-methoxyphenyl)-2-4-[2-formyl-( E )-vinyl]-2-methoxyphenoxy-propane- 1,3-diol, 1-(4-hydroxy-3-methoxyphenyl)-2-2-methoxy-4-[1-( E )-propen-3-ol]-phenoxy- propane-1,3-diol, 1-(4-hydroxy-3-methoxyphenyl)-2-(4-formyl-2-methoxyphenoxy)-propane-1,3-diol, 1,2-bis-(4-hydroxy-3-methoxyphenyl)-propane-1,3-diol and a trilignol, leptolepisol C.

Lignans and Brauns' Lignins from Softwoods

Various new dimeric. trimeric, and tetrameric lignans were isolated from the extractives of Larix leptolepis and their structures were elucidated. These lignans have the same linkage patterns äs those of the degradation products from softwood protolignin, but they are different from the lignin degradation products in optical activity. Existence of oligomeric and polymeric lignans is probable in the same fraction. Distributions of Brauns* lignin (BL) and milled wood lignin (MWL) in the cross section of trunks of Picea jezoensis and Larix leptolepis were determined and ccmpared with each other. From these results, it is concluded that BL may be a polymer fraction of Lignans and not a true lignin.

Degradation Products of Protolignin and the Structure of Lignin

A clue to the chemical structure of lignin was first given by the studies of K. Freudenberg and coworkers on the enzymatic dehydrogenation of coniferyl alcohol, in which several important di-, tri- and oligolignols were isolated and their structures were elucidated.11 A series of his studies threw light not only on the biogenesis but on the linkage types of lignin macromolecules. However, while precise information about lignin structure may be derived from various fragments of protolignins, it is also necessary to confirm the radical coupling mechanism for bond formation assumed by Freudenberg for these degradation products.