Two novel norditerpenoids, teucvin and teucvidin, were isolated from the neutral fraction of Teucrium viscidum Bl. var. Miquelianum (Maxim.) Hara (Labiatae). A partial structure A of teucvin was clarified by chemical means. The X-ray analysis of its heavy atom derivative 10 and subsequent chemical reactions led to assignment of the structure and absolute configuration 1 to teucvin. Comparison between several spectroscopic data of teucvidin with those of teucvin led to presumption that both compounds must be diastereomeric. Detailed NMR investigation of teucvidin using INDOR and NOE techniques resulted in assignment of its relative stereochemistry except C-12. Subsequently, the X-ray analysis of teucvidin itself by direct method elucidated its molecular structure. On the basis of these results, teucvidin was proved to have structure of 28 or its antipode. Finally, biogenesis of teucvin (1) is discussed.
