POLYMERIZATION OF BICYCLIC ACETALS .6. SYNTHESIS AND POLYMERIZATION OF (+)-(1R,5S)-6,8-DIOXABICYCLO[3.2.1]OCTANE

An optically active, stereoregular polyacetal possessing a backbone structure similar to that of natural dextran but opposite absolute configurations of the asymmetric carbons was newly prepared by the cationic polymerization of (+)-(1R, 5S)-6, 8-dioxabicyclo[3.2.1]octane (1*). The optically active monomer 1* was synthesized from sodium 3, 4-dihydro-2if-pyran-2-carboxylate (2) through the optical resolution of its diastereomeric dehydroabietylammonium carboxylate (4). Ring-opening polymerization of 1* was carried out in methylene chloride at -93, -78, and -30°C by using boron trifluoride etherate as an initiator. 1H-and 13C-NMR analysis of the resulting polymers revealed that highly stereoregular polymers were formed at -93 and -78°C. The polymer obtained at -93°C had a number average molecular weight of 6.8 × 104, melting at 172-175°C and showing a specific rotation of [α]33D-198° (chloroform). © 1979, American Chemical Society. All rights reserved.