We postulate that the polymerization proceeds by electrophilic aromatic substitution; the dihydroxy(methy1)sulfonium cation (3) formed by protonation of the oxygen atom of the sulfinyl group serves as the active species (Scheme 2). 3 4 CH3 Scheme 2. Possible polymerization mechanisin for the formation of 1.The formation of 3 requires a strong protic acid such as trifluoromethanesulfonic acid (pK, = -14.5).[13] The sulfonium cation 3 reacts with a benzene unit to form a hydroxy(methy1)phenylsulfonium cation (4>, and successive electrophilic substitution results in the formation of poly(methylsu1fonio-1,4phenylene salt). It has not been clarified why electrophilic substitution of 4 occurs at the para position.r141 The electron-donating property of the lone pair of the sulfonium group through 3d-2p resonance might predominate over the electron-withdrawing effect in a strongly acidic media in analogy to electrophilic substitutions with aromatic sulfoxide.[' Experimentul Procedure 1 . (Typical polymerization procedure): To a solution of benzene (0 47 g, 6 mmol) in

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256 unterschiedliche Trisaccharide aus nur 4 geschützten Grundbausteinen sind mit der hier vorgestellten Methode zur Synthese von Trisaccharidbibliotheken im Prinzip zugänglich. Die Methode nutzt eine latent aktive Glycosylierung; einen Eindruck von den in der Bibliothek enthaltenen Verbindungen gibt die Formel unten.

Proton and carbon chemical shift data and proton-proton coupling constants of the synthetic antithrombotic pentasaccharide SanOrg34006 and its synthetic precursors are reported. Long-range heteronuclear correlation experiments allow the determination of the substitution pattern of the protecting groups in the precursor molecules. Also, the sequence of the oligosaccharide was confirmed this way. The conformation of the a-L-iduronic acid moiety was studied by the analysis of the 3 J.

Microwave-Enhanced Goldberg Reaction: A Novel Route to N-Arylpiperazinones and N-Arylpiperazinediones.-The Goldbergtype arylation of structurally diverse amides (I) and (IV) is remarkably enhanced by microwave irradiation. -(LANGE, JOS H. M.; HOFMEYER, LOVINA J. F.; HOUT, FLORIS A. S.; OSNABRUG, STEFAN J. M.; VERVEER, PETER C.; KRUSE, CHRIS G.; FEENSTRA, ROLF W.; Tetrahedron Lett. 43 (2002) 6, 1101-1104; Res. Lab., Solvay Duphar B. V., NL-1380 DA Weesp, Neth.; EN)