ИСТИНА

Polycyclic ether marine natural product with the characteristic `ladder-like` trans-syntrans- fused structure have attracted interest from synthetic chemist for their unique, challenging molecular architecture and environmental impact. Traditional approaches to their syntheses have been based on construction of each cyclic ether one ring at a time, whereas the proposed biosynthesis is potentially more efficient, namely polyoxacyclization of a polyepoxide to furnish several rings in a single step [1]. Although the polyepoxide cyclisation has been known since 1990s, there are no publications for nitrogen contain substrates in this transformations. Herein we report our studies of Lewis acid mediated tandem oxacyclizations of polyepoxides contain fragment 1,2- aminoalcohols and geraniol units, leading to various product. The geraniol fragment was introduced via alkylation reaction with oxazolidin-2-one. After hydrolysis reaction with sodium hydroxide and subsequent protection (Boc- or Cbz-group) of secondary nitrogen atom chiral epoxidation was performed in presence of Shi ketone [2]. Subsequent tandem polyepoxide cyclisations at various conditions with different substrates led to formations of different type polycyclic scaffolds. Scope and limitations of the reactions are discussed. 1 McDonald, F.E.; Valentine, C.J.; Synlett 2006, 1816-1828 2 Wong, O.A.; Shi, Y.; Chem.Rev.2008, 108, 3958-3987