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Stereocontrolled total synthesis of the chiral building block (3S,4R)-3- [(R)-1-hydroxyethyl]-4-acetyloxy-azetidin-2-one: a useful synthon for the synthesis of (+)-thienamycin, carbapenems and penems.

Abstract A total stereocontrolled synthesis of ( 1 ), an intermediate in the synthesis of (+)-thienamycin, carbapenems and penems, based on a strategy that uses the S(-)hydroxy ethylbutyrate as chiral building block, is reported.

A synthetic approach to azetidinones from nitriles and lithiumtriethoxyaluminium hydride.

Abstract A convenient one-pot process for direct conversion of nitriles to 3,4-disubstituted azetidinones has been developed.

Preparation of 1,2 aminols from cyanohydrins viaN-diisobutylaluminium imines.

Abstract The N-Aluminium imines derived from cyanohydrins have been used in the synthesis of α-amino alcohols with high diastereoselectivity.

Polymer-supported phosphonates. Olefins from aldehydes, ketones, and dioxolans by means of polymer-supported phosphonates

Phosphonates substituted with electron-withdrawing groups (CN and CO2Me) have been supported, by means of a neutralization reaction, on the macroreticular anion-exchange resin Amberlyst A-26. Treatment of carbonyl compounds with the polymer-bound phosphonate in various solvents gave olefins in high yields, at room temperature. Either batch or column techniques are employed, the latter offering the opportunity of a continuous procedure. The simultaneous use of the phosphonate resin and of an acidic one (Amberlyst 15 H) allowed the direct sequential hydrolysis and olefination of dioxolans.

A facile synthesis of cephem side chains by palladium catalyzed cross-coupling of 3-substituted-Δ3-cephems with dialkylzinc or vinyltributyltin

Synthesis of 3-vinyl- and 3-alkyl-Δ3-cephems was performed in a regioselective manner by palladium acetate catalyzed reaction of 3-sulfonato- or 3-bromo-Δ3-cephems with dialkylzinc or vinyltributyltin. A new access to 3-alkyl-Δ3-cephems is opened, starting from the allenyl compound 10.

Reaction of silylimines with ester enolates. Synthesis of N-unsubstituted azetidinones starting from nitriles

The reduction of aromatic, vinylic, and aliphatic nitriles with several ‘metal–aluminium hydrides’ produces an addition product which is readily converted to a β-lactam derivative by treatment with Me3SiCl followed by the addition of lithium ester enolates. The factors influencing the course of the cycloaddition-type reaction are discussed. A relatively simple synthetic procedure for the preparation of N-unsubstituted azetidin-2-ones in satisfactory yields is reported.

Synthesis of compounds containing the isoprene unit. A new stereoselective synthesis of all-trans vitamin A and of methyl (2E,4E)-3,7,11-trimethyldodeca-2,4-dienoate

Methyl (2E,4E)-3,7,11-trimethyldodeca-2,4-dienoate (8b), a potent insect growth regulator, is synthesized from the dianion of 3-methylbut-3-en-1-ol (2) and tetrahydrocitral (3). Elimination of acetic acid to (8b) in (2E,4E) configuration is achieved by treatment of the intermediate acetoxy-ester (7b) with a base (NaH, KH, or ButOK) in the presence of a catalytic amount of crown ether in hexane. Following the same scheme, a new synthesis of Vitamin A via all-trans retinal is achieved.

A new synthesis of 1-t-butyldimethylsilyl-3-acetyl-4-carboxyazetidin-2-one

A practical stereoselective synthesis of the title compound (1)via titanium tetrachloride mediated alkylation of the silyl enol ether of ethyl acetoacetate is described.

Polymer-supported reagents: polar effects in substrate selectivity

A remarkable selectivity effect has been observed in the competitive reaction of a polymer-supported nucleophile with pairs of halides of analogous size and different polarity.