Synthesis of Psoralens

Psoralens, also known as furanocoumarins and coumarine derivatives, are naturally occurring or synthetic tricyclic aromatic compounds. They reveal interesting photobiological activities such as skin photosensitization, characterized by the onset of erythema followed by dark pigmentation. The related angular isomers, namely angelicin, are also present in plants and have been chemically synthesized [1]. Psoralens are also of interest because they are used as a probe in molecular biology and nucleic acid chemistry [2]. Coumarins can be classified in the latter group [3]. In this paper we discuss the synthesis of psoralens (Scheme I and II). Currently there is only one report of antifungal activity reported for angular coumarins [4–5]. As part of our ongoing research program to identity chemical and/or biomarkers of dietary supplements we have synthesized a series of psoralens for biological evolution.

Acknowledgements: The work was supported by the United States Department of Agriculture, Agricultural Research Service Specific Cooperative Agreement Number 58-6408-06-067. Thanks to Dr. Barathi Avula for HRESIMS and Dr. Vaishali C Joshi for plant identification at the National Center for Natural Products Research. References: [1] Wulff WD, et al. (1988), J Am Chem Soc. 110: 7419–34. [2] Cimino GD, et al. (1985) Ann Rev Biochem 54: 1511–93. [3] Moor ACE, Gasparro FP, (1996) Clin Dermatol, 14: 353–365. [4] Grayer RJ, Harborne JB, (1994) Phytochemistry, 37: 19. [5] Chimichi S, et al. (2002) Tetrahedron 58: 4859–4863.