ABSTRACT
The term lignan was used to describe a group of natural products that are primarily derived from the oxidative coupling of phenylpropanoid units. Lignans are usually phenylpropanoid dimers. In 1961, Freudenberg, et al. numbered the phenylpropanoid C6-C3 carbon skeleton as 1-9, and the C6-C3 unit as 1′-9′. Lignans are usually referred to as dimers of phenylpropanoids, linked by β-β′ (8-8′) (1)[3]. Gottieb coined the term neolignan for compounds composed of two phenylpropanoid units that are linked other than by the C8-C8′ (2)[4]. Later, he also coined the term oxyneolignans for such lignans whose two C6-C3 units were linked by oxygen (3).
