Design and synthesis of fused and bridged tetrahydropyran tetrahydrofuran systems trough prins type cascade cyclization

Abstract

In organic synthesis, development of novel strategies for heterocyclic compounds is an newlineimportant goal as many of such compounds display valuable properties. Six-membered newlineoxygen, nitrogen and sulfur containing heterocycles are widely recognized as very newlineimportant scaffolds in many areas of bio-organic and medicinal chemistry. In particular, newlinethe tetrahydropyran ring is featured in a variety of biologically active natural products, newlinemarine toxins, and pheromones.1Among various tetrahydropyran ring containing newlineClavosolides(1), Calyxin(2), Phorboxazoles(3), Centrolobine(4), Laulimalide(5), newlineKendomycin(6), Leucascandrolide(7) and Polycavernoside(8) are the most important in newlineview of their inherent biological activity.(Figure 1).Therefore it is important to design newlinenew and efficient strategies towards such particularly attractive target molecules. Several newlinemethods have been devised for construction of tetrahydropyran and piperidine rings. newlineThese methods mainly include Prins cyclization,2 hetero-Diels-Alder cycloaddition,3 newlineheterocyclization of epoxides and aziridines,4 Pictet-Spengler cyclization,5 Petasis-Ferrier newlinerearrangement,6 oxa- and aza-Micheal addition,7 cyclization through oxidative carbonhydrogen newlinebond fuctionalization,8 ring closing methathesis9 etc. During past decades, newlinerapid advancement has been made in this area by various research groups. In this chapter, newlinewe present a brief review of the Prins cyclization reaction, focusing on new newlinemethodologies development and applications to natural product synthesis, as a newlinebackground that led us to choose this reaction as a key topic for our research. The brief newlinereview is discussed about Prins cyclization. newline