9-Norlignans: Occurrence, Properties and Their Semisynthetic Preparation from Hydroxymatairesinol.

Patrik Eklund,Jan-Erik Raitanen

doi:10.3390/molecules24020220

Abstract

Lignans, neolignans, norlignans and norneolignans constitute a large class of phenolic natural compounds. 9-Norlignans, here defined to contain a β–β’ bond between the two phenylpropanoid units and to lack carbon number 9 from the parent lignan structure, are the most rarely occurring compounds within this class of natural compounds. We present here an overview of the structure, occurrence and biological activity of thirty-five 9-norlignans reported in the literature to date. In addition, we report the semisynthetic preparation of sixteen 9-norlignans using the natural lignan hydroxymatairesinol obtained from spruce knots, as starting material. 9-Norlignans are shown to exist in different species and to have various biological activities, and they may therefore serve as lead compounds for example for the development of anticancer agents. Hydroxymatairesinol is shown to be a readily available starting material for the preparation of norlignans of the imperanene, vitrofolal and noralashinol family.

Highlights

Many secondary metabolites, including lignans, flavonoids, and coumarins are formed from phenylpropanoids originating from the well-known shikimic acid pathway
In this paper we review the occurrence and properties of natural compounds belonging to the class of 9-norlignans, and in addition, we report the semisynthesis of
We have shown that hydroxymatairesinol is degraded to norlignan derivative 15 by strong alkali

Summary

Introduction

Many secondary metabolites, including lignans, flavonoids, and coumarins are formed from phenylpropanoids originating from the well-known shikimic acid pathway. Norlignans, a subclass of lignans lacking one or more carbon atoms, seem to be a rather unknown class of natural products. Compared to other phenylpropanoids their occurrence, biosynthetic pathway, and their properties are much less reported in the literature. 9-norlignans (lacking carbon 9 from the parent lignan skeleton) with guaiacyl (3-methoxy-4-hydroxyphenyl) moieties have rarely been reported in the literature, they would be expected to be common norlignans as guaiacyl lignans are the most abundant class of lignans. Common substitution patterns are found in norlignans, but the more rare 2,4,5-trisubstituted phenyl moieties seem to be present in several 9-norlignans. In this paper we review the occurrence and properties of natural compounds belonging to the class of 9-norlignans, and in addition, we report the semisynthesis of

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Conclusion