Diastereoselective synthesis of 2,3,4-trisubstituted γ-lactols and γ-lactones via regio- and stereocontrolled opening of a 1,2-epoxy-4-hydroxyalkyl carbamate with hetero-nucleophiles

✍ Scribed by Jörg Lüßmann; Dieter Hoppe; Peter G. Jones; Christa Fittschen; George M. Sheldrick

• Publisher: Elsevier Science
• Year: 1986
• Tongue: French
• Weight: 227 KB
• Volume: 27
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)84858-3

✦ Synopsis

The acid-catalyzed ring opening of the title epoxide 1 takes place at the C-l atom with retention of configuration at C-2 to form 2,3-cis-2-hydroxy-substituted y-lactol deriva= tives 3 In basic media, nucleophiles attack the C-Atom with inversion of configuration yielding 2,3-trans-lactols 5. Oxidation furnishes corresponding y-lactones 6, 11 or 13. Diastereomerically pure 1,2-epoxy-4-hydroxyalkyl carbamates of type 1 are readily prepared from 2-alkenyl carbamates and aldehydes 1) , with formation of the C-3 -C-4 bond. Since both synthetic steps (titanium-mediated homoaldol reaction 2) and hydroxyl-directed epoxidation) proceed with essentially complete diastereoselectivities, no isomer separations are ne= cessary. The oxy-substituted oxirane ring in 1 constitutes an activated cr-hydroxy carbonyl moiety. Among