For the first time, a reliable procedure for synthesizing new acidic polyelectrolyte-containing amphiphilic conetworks (APCNs), poly(methacrylic acid)-l-polyisobutylene (PMAA-l-PIB), is described. The thorough characterization of the synthesis products is also presented through elemental analysis, differential scanning calorimetry (DSC), and basic swelling studies. Three series of APCNs were successfully synthesized in wide composition ranges by the macromonomer method using exact bifunctional methacrylate-telechelic PIB cross-linkers (MA−PIB−MA) of three different molecular weights (M n):  2000, 5000, and 13000. The MA−PIB−MA macromolecular cross-linkers were prepared via quasiliving carbocationic polymerization. To prevent phase separation and thus insufficient network formation during synthesis, the conetworks were synthesized by thermally initiated free radical copolymerization of MA−PIB−MA and trimethylsilyl methacrylate, a hydrophobized precursor of methacrylic acid. After the next critical synthetic step, the quantitative hydrolytic cleavage of the trimethylsilyl groups from the poly(trimethylsilyl methacrylate) chains in the resulting precursor conetworks, 5−8 different compositions of each PMAA-l-PIB conetwork series were obtained. The low amounts of extractables (<8−10%) and elemental analysis data showed high copolymerization yields and close to target compositions. DSC investigations indicated phase separation of the PMAA and PIB components. As all PMAA-l-PIB conetworks are optically clear materials, the extent of phase separation must occur on the nanometer scale. The amphiphilic character of these new materials was demonstrated by uniform swelling of PMAA-l-PIB conetworks in both aqueous and apolar media which indicates cocontinuous nanophasic morphology.

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Completely reversed stereoselectivity of reduction of methyl 6-deoxy-2,3-O-isopropylidene-3-C-methyl-α-L-mannopyranoside (2) and its deisopropylidenated derivative (7) was observed. Compound 2 gave exclusively the L-talo-isomer (3) with NaBH 4 in MeOH, but the reduction of 7 with NaBH 4 in acetic acid resulted in the L-mannoderivative 8. It is assumed that in the first case the stereoselectivity is determined by the steric accessibility of the carbonyl group, while in the second case free OH-groups direct the selectivity of the reduction by complexation or ligand exchange.Members of the Mycobacterium avium serocomplex 1,2 are opportunistic pathogens and can cause serious infections. Structural analysis of the cell-surface glycopeptidolipid-type (GPL) antigen of serovar 19 showed that it contains the O-linked pentasaccharide 1 3 . While most of the structural features of the penultimate residue ( Fig.) have been determined, ambiguity persists regarding the stereochemistry at C-4 of this unit.Here we report stereoselective syntheses of both epimers (6, 12) of the unidentified unit as their methyl glycosides in the proposed, α anomeric forms 3 . Precursor to both targets was methyl 6-deoxy-2,3-Oisopropylidene-3-C-methyl-α-L-lyxo-hexopyranosid-4-ulose (2) that was prepared as described by Klemer from L-rhamnose in four steps 4 . Reduction of compound 2 either with NaBH 4 or with LiAlH 4 (Scheme) resulted in the 6-deoxy-L-talo isomer 3 exclusively, as confirmed by the low value (1 Hz) of the 3 J 4,5 coupling constant. The complete stereoselectivity of this reduction can be explained by the extremely crowded β-(L) side of compound 2: the hydride anion can approach the C-4 carbon atom only from the α-(L) face. Methylation of compound 3 resulted in 4 from which the isopropylidene group was removed by acidic hydrolysis to obtain 5. Methylation of the axial OH-2 of 5 required rather drastic conditions to give 6, and formation of the fully methylated product (13) was also observed (15 %). Compound 13 exists exclusively in 4 C 1 (L) conformation. SchemeFigure Downloaded by: York University libraries. Copyrighted material. LETTERS SYNLETTTo prepare the rhamno-isomer (12) from compound 2, its isopropylidene group was hydrolyzed, then the free ulose-derivative (7) was treated with NaBH(OAc) 3 (Scheme 1) 5,6 . Methyl α-Levalopyranoside was isolated in nearly quantitative yield. In its 1 H-NMR spectrum H-4 gave a doublet at 3.39 ppm having 3 J 4,5 10 Hz, that confirms the trans-diaxial relationship of the H-4 and H-5 protons. The completely reversed stereoselectivity compared to the reduction of 2 could only be achieved in the presence of the free OH groups suggesting that these play a role in the complexation of the hydride donor thus governing the direction of the attack of the hydride anion. Isopropylidenation of 8 gave compound 9 and after methylation (→10) and deprotection (→11) the resulting diol was selectively methylated at OH-2 at 0 °C under phase-transfer conditions. The isolated yield of compound 12 was 67 % after chro...