Novel Amidoalkylation of 4-Acetoxyazetidinones with Allylic Boranes. A Stereoselective Entry into the Tribactams

Pd(0)/InI-mediated allylic additions to 4-acetoxy-2-azetidinone: new route to highly functionalized carbocyclic scaffolds

Acylnitroso-derived hetero-Diels-Alder cycloadducts are susceptible to C-O bond cleavage with Pd(0) and InI to form allylic indium(III) species. The in situ prepared allylindium compounds readily react at room temperature with Eschenmoser's salt. Allylation of 4-acetoxy-2-azetidinone provides derivatized cyclopentenes in high regio- and diastereoselectivity.

The synthesis and in vitro testing of structurally novel antibiotics derived from acylnitroso Diels–Alder adducts

The structural similarity between beta-lactam antibiotics, such as penicillin, and isoxazolidine-3,5-dicarboxylic acids led to the hypothesis that isoxazolidine-3,5-dicarboxylic acids could be effective analogs of beta-lactam antibiotics. The syntheses of relevant isoxazolidine-3,5-dicarboxylic acids from acylnitroso Diels-Alder adducts and subsequent biological testing have shown that these first examples are inhibitors of Escherichia coli X580.

A Practical and Facile Synthesis of Azetidine Derivatives for Oral Carbapenem, L-084

An orally active carbapenem L-084, which exhibits high bioavailability in humans, has a 1-(1,3-thiazolin-2-yl)azetidin-3-ylthio moiety at the C-2 position of the 1beta-methylcarbapenem skeleton. We established a practical and cost-effective synthesis of 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (1) for further scale-up production of L-084. This synthesis method entails an industry-oriented reaction of azetidine ring-closure to yield N-benzyl-3-hydroxyazetidine (16), which is eventually converted to 1 via key intermediates, Bunte salts 19 and 20.

Practical synthesis of (R)-4-mercaptopyrrolidine-2-thione from L-aspartic acid. Preparation of a novel orally active 1-beta-methylcarbapenem, TA-949

A facile and economical synthesis of a novel orally active 1-beta-methylcarbapenem, TA-949 (1), is described. The key process involves an efficient synthesis of the C-2 side chain (R)-4-mercaptopyrrolidine-2-thione 2 from L-aspartic acid and the construction of the 1-beta-methylcarbapenem skeleton. The mercapto group of 2 with an R-configuration was formed via deaminative bromination of the amino group of L-aspartic acid beta-methyl ester hydrochloride 12 followed by a complete S(N)2-type substitution with potassium benzenemethanethiolate. High-yield amination and cyclization of the chloride 15 to the pyrrolidin-2-one 16 was accomplished by a simple treatment with ammonia. Thiation of 16 and the Birch reduction of the resultant thiolactam 18 provided the C-2 side chain 2 in high yield with the asymmetric center retained as such. The side chain 2 was installed into the 1-beta-methylcarbapenem skeleton either by coupling with the vinyl phosphate 5 or by the use of the counterattack strategy involving the Dieckmann-type cyclization of the thioester 8. Removal of the protective groups of the coupling product 6 followed by esterification provided TA-949 (1) in high yield.