Zbigniew Kałuza

Polish Academy of Sciences, Warszawa, Masovian Voivodeship, Poland

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Publications (7)20.32 Total impact

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    ABSTRACT: The synthesis of oxacephalotin and oxacephamandol, which are more active than natural, sulfur-containing congeners, and the isolation of clavulanic acid, a potent inhibitor of beta-lactamase enzymes, directed attention of many academic and industrial laboratories the synthesis of oxygen analogues of penicillins and cephalosporins. The present review focuses attention on the problem of stereocontrol in the formation of a desired configuration of the bridgehead carbon atom in the title compounds. Five feasible synthetic methods leading to the basic skeletons of clavams and 5-oxacephams are discussed. Three of them involve the nucleophilic substitution at C-4 of the azetidin- 2-ones performed as inter- or intramolecular process and the remaining two involve cycloaddition reactions between ketenes and iminoethers, or between vinyl ethers and isocyanates. Owing to the general application, stereospecificity and high asymmetric induction, the last method seems to be most advantageous. The weak point of the nucleophilic substitution methodology is that a nucleophile approaches the 3-substituted azetidin-2-one ring preferentially anti to the existing substituent and in the case where there is no substituent at C-3, that the stereoselectivity of formation of the new chirality center at C-4 is low. All discussed methods are illustrated by the examples taken from the literature.
    No preview · Article · Aug 2004 · Current Medicinal Chemistry
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    ABSTRACT: The relationship between chiroptical properties of differently substituted 5-dethia-5-oxacephams and their respective molecular structures was investigated. The amide chromophore of the beta-lactam unit in these compounds was found to be nonplanar with a shallow pyramidal configuration at the nitrogen atom. Due to the nonplanarity, the beta-lactam system becomes inherently dissymmetric, which is supported by a high magnitude of the n --> pi* CD band. It was also found that the helicity of the lactam moiety in investigated oxacephams is controlled by the absolute configuration at the C(6) carbon atom. On this basis, a helicity rule correlating a positive (negative) sign of the n right arrow pi Cotton effect with a negative (positive) O [double bond] C [bond] N [bond] C(6) torsional angle for policyclic beta-lactam derivatives possessing a nonplanar amide chromophore was formulated.
    No preview · Article · Apr 2002 · The Journal of Organic Chemistry
  • Zbigniew Kałuza · Sang-Hyun Park
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    ABSTRACT: [2+2]Cycloaddition of chlorosulfonyl isocyanate (CSI) to benzylvinyl or divinyl ethers provides new attractive β-lactam building blocks which are subjected to N-alkylation followed by the oxidation of the substituent at C-4 and afford the corresponding 4-acyloxy-N-substituted azetidin-2-ones, suitable for nucleophilic displacement at the C-4 carbon atom.
    No preview · Article · Sep 1996 · Synlett
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    ABSTRACT: [2+2] Cycloaddition of tosyl isocyanate to sugar vinyl ethers followed by N-deprotection affords β-lactams with fairly good asymmetric induction.
    No preview · Article · Dec 1989 · Tetrahedron Letters
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    ABSTRACT: Glycolic cleavage of the vic-diol grouping present in N-benzyl-2-carboxy-2-deoxypento and hexopyranosylaminolactams (, , and ) with sodium metaperiodate under standard conditions leads to formation of reactive dialdehydes and 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 and with sodium borohydride gives optically pure 3,4-disubstituted azetidinones , , , and which can serve as starting materials for the synthesis of 1-oxabicyclic β-lactams.
    No preview · Article · Jan 1989 · Tetrahedron
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    ABSTRACT: N-Benzyl-2-carboxy-2-deoxypento and hexopyranosylaminolactams readily available via addition of trichloroacetyl isocyanate to substituted glycals, were transformed into enantiomerically pure N-benzyl-4-alkoxy-3-hydroxymethylazetidinones-2. The transformation involved the glycolic cleavage which was followed by sodium borohydride reduction. The above compounds can serve as starting materials for the synthesis of 1-oxapenams and 1-oxacephems.
    No preview · Article · Dec 1987 · Tetrahedron Letters
  • Marek Chmielewski · Zbigniew Kałuza
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    ABSTRACT: Cycloaddition of trichloroacetyl isocyanate to 1,5-anhydro-2-deoxy-d-erythro- and -l-threo-pent-1-enitols, and 1,5-anhydro-2-deoxy-d- and -l-arabino-hex-1-enitols having benzyl, methyl, tert-butyldimethylsilyl, and trimethylsilyl substituents on hydroxyl groups proceeds satisfactorily, under normal pressure at room temperature, to give a mixture of [2 + 2] and [4 + 2] cycloadducts. The isocyanate enters the glycal molecule stereospecifically anti with respect to the C-3 substituent. Bicyclic adducts slowly rearrange to the respective α,β-unsaturated amides. N-Deprotection of the trichloroacetyl substituent in [2 + 2] cycloadducts produces stable β-lactams. Further deprotection gives crystalline, water-soluble 2-carboxy-2-deoxypento- and -hexo-pyranosylaminolactams having a unique bicyclic sugar structure.
    No preview · Article · Sep 1987 · Carbohydrate Research