Jacek Grodner

An Improved Synthesis and NMR Spectra of Benzylated Glycals

Abstract Benzylated glycals, unlike their acylated congeners which easily undergo allylic rearrangement, are frequently employed as reactive enol ether type substrates in a variety of electrophilic addition reactions.1–4 Although these compounds are considered to be readily available substrates, reported procedures for their syntheses involve some steps of limited efficiency, chromatographic separations or costly reagents,5–7 and experimental requirements not amenable for large scale preparations. In view of the recent applications of benzylated glycals to syntheses of O-glycosides,1,2 C-glycosyl compounds,3 and β-lactams,4 we have undertaken a study aimed at efficient one step benzylation procedures applicable to pyranoid 1-enitols as well as to their acylated derivatives. This goal was eventually achieved by employing a catalytic phase transfer alkylation system with

Optically pure 3,4-disubstituted azetidinones from sugars

Abstract Glycolic cleavage of the vic -diol grouping present in N -benzyl-2-carboxy-2-deoxypento and hexopyranosylaminolactams ( 5 , 6 , and 7 ) with sodium metaperiodate under standard conditions leads to formation of reactive dialdehydes 13 and 14 which upon standing undergo intramolecular aldol condensation to afford bicyclic β-lactams having a four-membered ring fused to the furanoid system. Reduction of dialdehydes 13 and 14 with sodium borohydride gives optically pure 3,4-disubstituted azetidinones 15 , 17 , 19 , and 20 which can serve as starting materials for the synthesis of 1-oxabicyclic β-lactams.

Synthesis of (3R,5S,6R) 2,6-Diacetoxymethylclavam from D-Galactal

Abstract N- (t-Butyl)dimethylsilyl-2- C: 1 - N- car bony 1 - 2 -deoxy- α-D-galactopyran-osylamine (1) was tritylated and the product was subjected to a glycolic cleavage to give dialdehyde 10. Subsequently, compound 10 was transformed into bromide 14 using standard procedures. The fluoride anion induced cyclization in 14 afforded clavam 15.

Synthesis of (6R) 4-t-butoxycarbonyl-7-hydroxymethyl-1-oxa-3-cephem from d-arabinal

Abstract Readily available from 3,4- di -O- trimethylsilyl- d -arabinal (13) bicyclic β-lactam 14 was converted into ylide 17 which was subsequently desilylated and subjected to glycolic cleavage of the vic-diol grouping. Dialdehyde 19 spontaneously cyclizied to a 1-oxacephem skeleton 16 which was subsequently reduced to t-butyl 7-hydroxymethyl-1-oxa-3-cephem-4-carboxylate (21).

An attempt on the synthesis of the clavam skeleton from glycals and isocyanates

Abstract N -Protected 2-C:1- N -carbonyl-2-deoxy-glycopyranosylamines 12 , 13 , and 16 were subjected to the two-step oxidation to afford dicarboxylic acids 20 , 21 , and 30 . Decarboxylation of the group located in a malonyl system with the β-lactam carbonyl group failed to give 1,4-disubstituted azetidinones. Bromides 45 , 46 , obtained from 30 by standard transformations, subjected to fluoride-anion-induced cyclization, failed to form clavam 53 .