J. Appl. Cryst.の発刊に際して

Asymmetric 1,3-Dipolar Cycloaddition Reactions

Synthesis of Heterocycles via Palladium-Catalyzed Carbonylations

Transition metal chemistry of cyclopropenes and cyclopropanes.

Bull. Chem. Soc. Jpn. への投稿のすすめ

Heterocycles from alkylidenecyclopropanes.

2.1.5. Electrophilic Attack on CdC 3994 2.1.6. NH Insertions in Diazo Compounds 3994 2.1.7. Pd Catalyzed Cyclizations 3994 2.2. Cyclizations by C-C Bond formation 3995 2.2.1. Nucleophilic Displacement of Halides 3995 2.2.2. Cyclizations Involving CdO Group 3995 2.3. Cycloadditions 3996 2.4. Ring Rearrangements 3997 2.4.1. Rearrangements of Four-Membered Rings 3997 2.4.2. Rearrangements of Larger Rings 3998 2.5. Reduction of Azetidin-2-ones 3998 2.6. Miscellaneous Syntheses 3999 2.7. Important Classes of Compounds 4000 2.7.1. Natural Products 4000 2.7.2. Azetidine Carboxylic Acids 4001 2.7.3. Exomethylene Azetidines 4002 2.7.4. Ligands for Metal-Catalyzed Reactions and Chiral Auxiliaries 4003

Novel syntheses of azetidines and azetidinones.

The synthesis of polyhydroxylated indolizidines and pyrrolizidines belonging to the class of iminosugars, endowed with a vast and assorted biological activity, can be achieved in a straightforward manner by a general strategy consisting of a highly stereoselective 1,3-dipolar cycloaddition of polyhydroxylated pyrroline-N-oxides followed by simple transformations of the isoxazolidine adducts The strategy allows the complete control of the relative and absolute stereochemistry of the numerous stereogenic centers decorating these compounds

Stereocontrolled Cyclic Nitrone Cycloaddition Strategy for the Synthesis of Pyrrolizidine and Indolizidine Alkaloids

Progress in the synthesis and transformations of alkylidenecyclopropanes and alkylidenecyclobutanes.

The structure and absolute configuration of natural lentiginosine isolated from plant sources was determined to be (1S,2S,8aS)-1,2-dihydroxyindolizidine ((+)-4) on the basis of the synthesis of both enantiomers (+)-4 and (-)-4 and their inhibition of amyloglucosidases. Alkaloid (+)-4 was derived from (L)-(+)-tartaric acid via a highly stereo- and regioselective 1,3-dipolar cycloaddition of (3S,4S)-3 ,4-bis[(tert-butyldiphenylsilyl)oxy]-1-pyrroline N-oxide to methylenecyclopropane, followed by thermal rearrangement of the adduct into (1S,2S,8aS)-1,2-[(tert-butyldiphenylsily)oxy]octahydroindolizin-7-one. The enantiomer (-)-4 was derived in the same way from (D)-(-)-tartaric acid. Both (+)-4 and (-)-4 displayed inhibition specificity for amyloglucosidases, being inactive toward 17 other glycosidases. With amyloglucosidase from Aspergillus niger, synthetic (+)-4 displayed inhibition (K-i = 2 mu M) 5 times stronger than that reported for natural lentiginosine, 35 times that measured for (-)-4, and twice that of castanospermine. Alkaloid (+)-4 is thus the most potent and specific competitive inhibitor of amyloglucosidases among azasugars and their analogues.

Franca M. Cordero

Papers

Heterocycles from alkylidenecyclopropanes.

Novel syntheses of azetidines and azetidinones.

Stereocontrolled Cyclic Nitrone Cycloaddition Strategy for the Synthesis of Pyrrolizidine and Indolizidine Alkaloids

Progress in the synthesis and transformations of alkylidenecyclopropanes and alkylidenecyclobutanes.

Assignment of the Absolute Configuration of Natural Lentiginosine by Synthesis and Enzymic Assays of Optically Pure (+) and (-)-Enantiomers