Stereoselective Synthesis of 3-Oxygenated-cis-dialkyl-2,5-substituted Tetrahydrofurans from Cyclohexadienediols
摘要:
The 3-oxygenated-cis-dialkyl-2,5-substituted tetrahydrofuran system, present in several natural products, was prepared with good selectivity by acidic cyclization of 5-alkene-1,2,4-triol derivatives. The starting alkenol was obtained in few steps from a chiral cis-diol resulting from microbial oxidation of bromobenzene. The study of the cyclization allowed the rationalization of all experimental results by assuming a complete ionization at the allylic position and a model close to the one proposed by Labelle for homoallylic induction in five-membered ring closures.
The totalsynthesis of the anticancer marinenaturalproduct mycalol has been achieved using a Maruoka asymmetric allylation, a Noyori asymmetric reduction, an asymmetric alkynylation, and a zipper reaction as key steps.