Primary and Secondary Allyltitanium(IV) Reagents in Aldehyde Allylation II: Application to an Enantioselective Preparation of a C1-C7 Fragment of Spiramycin
A syntheticapproach to the eastern part of spiramycin, an important antibiotic compound, is described. Introduction of the side chain was first envisaged through a Hoppe aldehyde allylation. This reaction was carried outbetween an optically pure aldehyde 32 and a (′)-γ-alkoxy allyltitanium(IV) species derived from a primary γ-alkoxy allyl (diisopropyl)carbamate. Under kinetic resolution conditions