Showing papers by "Carlos del Pozo published in 2002"

Staudinger reactions of unsymmetrical cyclic ketenes: a synthetically useful approach to spiro β-lactams and derivatives. Reaction mechanism and theoretical studies

Abstract: An efficient and operationally simple synthesis of tetrahydrofuran-derived spiro-β-lactams using the ketene–imine cycloaddition route is described. Also the preparation of spiro-N-sulfonyl-β-lactam derivatives, which are analogs of monobactams, is reported. As far as we know, this is the first time that an unsymmetrical cyclic ketene is used in a Staudinger-type reaction. The experimental evidence suggests the involvement of a ketene derived from the acyl chloride precursor in the reaction. High-level ab initio calculations have been performed in order to get insight into the electronic effects controlling the stereochemical outcome of the reactions.

Synthesis of α,α-Disubstituted β-Amino Esters and Peptide Derivatives

Abstract: The synthesis of a,a-disubstituted β-amino esters and peptide derivatives from readily available 4-spiro-β-lactams 1 is described. The geminally disubstituted β-amino esters are obtained from the N-Boc spiro β-lactams 2 by treatment with potassium cyanide in methanol. Alternatively, the use of spiro β-lactams 2 as acylating agents of the amino group of C-protected amino acids, allowed its direct incorporation into a peptidic chain.

Staudinger Reactions of Unsymmetrical Cyclic Ketenes: A Synthetically Useful Approach to Spiro β‐Lactams and Derivatives. Reaction Mechanism and Theoretical Studies.

Abstract: An efficient and operationally simple synthesis of tetrahydrofuran-derived spiro-β-lactams using the ketene–imine cycloaddition route is described. Also the preparation of spiro-N-sulfonyl-β-lactam derivatives, which are analogs of monobactams, is reported. As far as we know, this is the first time that an unsymmetrical cyclic ketene is used in a Staudinger-type reaction. The experimental evidence suggests the involvement of a ketene derived from the acyl chloride precursor in the reaction. High-level ab initio calculations have been performed in order to get insight into the electronic effects controlling the stereochemical outcome of the reactions.

Variolin derivatives and their use as antitumor agents

Abstract: Variolin derivatives of formula (5) are provided, wherein the substituent groups defined by X2, R1, R2, R3, R6, R7 and R12 are each independently selected from the group consisting of H, OH, OR', SH, SR', SOR', SO2R', NO2, NH2, NHR', N(R')2, NHCOR', NHSO2R', CN, halogen, =O, C(=O)H, C(=O)R', CO2H, CO2R', carboxyalkyl, C1-C12 alkyl, C2-C12 alkenyl, C2-C12 alkynyl, substituted or unsubstituted aryl, substituted or unsubstituted aralkyl and substituted or unsubstituted heteroaromatic; wherein each of the R' groups is independently selected from the group consisting of H, OH, SH, N02, NH2, CN, halogen, =O, C(=O)H, C(=O)CH3, CO2H, CO2CH3, C1-C12 alkyl, C2-C12 alkenyl, C2-C12 alkynyl, aryl, aralkyl and heteroaromatic; wherein the pairs of groups R1 and R2, R2 and R3, R3 and R12, R12 and R6, or R6 and R7 may be joined into a carbocyclic or heterocyclic ring system.

Synthesis of α,α-Disubstituted β-Amino Esters and Peptide Derivatives.

Abstract: The synthesis of a,a-disubstituted β-amino esters and peptide derivatives from readily available 4-spiro-β-lactams 1 is described. The geminally disubstituted β-amino esters are obtained from the N-Boc spiro β-lactams 2 by treatment with potassium cyanide in methanol. Alternatively, the use of spiro β-lactams 2 as acylating agents of the amino group of C-protected amino acids, allowed its direct incorporation into a peptidic chain.