A stereoselective synthesis of the C21 C27 fragment of phorboxazoles A and B was achieved in 12 linear steps via an intramolecular cyclization induced by mercury acetate, to afford a functionalized tetrahydropyran. © 2003 Elsevier Science Ltd. All rights reserved.

Platinum(II) and an unusual cationic gold(I) complex were identified as mild catalysts for the room temperature cycloisomerization or tandemhydroalkoxylation/acetal formation of unactivated internal alkynols. Under the appropriate conditions, 5-endo, 5-exo, 6-endo, and 6-exo cycloisomerization modes are all available.

A strategy of tandem ketene-trapping/IMDA toward the total synthesis of the hirsutellones was attempted. The AB ring moiety of the hirsutellones was constructed with the proper tereochemistry.

Depending on the nature of the metal catalyst, ω-hydroxy propargylic acetates choose between alternative cycloetherification manifolds to produce functionalized heterocycles in high yields. AuCl catalyzes the formation of oxacyclic enol acetates, whereas [Cl2Pt(CH2CH2)]2 (Zeise’s dimer) will induce a propargylic substitution via an unprecedented SN2′-type allenic substitution from within a chelated square planar cationic Pt(II) complex.

An asymmetric synthesis of the backbone of the core of natural peloruside A is described. Key elements include reiterative application ofenantioselective allylation to establish the stereochemistry of the backbone and a double asymmetric aldol reaction to successfully couple two fragments.