An effective and stereoselective synthesis of 3-(1'-methyl/phenylallyl)-3-phenylthio-β-lactams (3/4) using substituted allylsilane and Lewis acid is described. The reaction leads to the formation of a mixture of C-3 substituted allyl β-Lactams. However, these compounds on desulphurisation using tri-n-butyltinhydride and Raney Ni provide two separable diastereomers of the reduced product.

Medicinal chemistry of heterocycles especially b-lactams have been an important discovery in today’s mankind. b-Lactam nucleus is structural feature and core of the biological activity of one of most successful classes of therapeutics to date characterized by a broad spectrum of activity and low toxicity. It constitutes classes of drugs that includes the antibiotics like penicillins, cephalosporins, clavulanic acid, monobactams and also shows wide range of important biological activities such as anti-cancer, anti-inflammatory and anti-malarial. The monocyclic b-lactams and their hetero-substituted conjugates are also applied for the synthesis of many classes of compounds which include taxol derivatives, alkaloids and amino acids. Antimicrobial resistance is one of the major and growing concerns in hospital and community acquired infections and new anti-microbial agents are therefore urgently required. So now, the organic chemists have focussed on the modification of existing molecules for the synthesis of new compounds having diverse pharmacological activities with broad spectrum activity. Monocyclic b-lactams are stable to hydrolysis by blactamases in comparison to other b-lactams and thus are attractive platform for searching anti-bacterial agents. The discovery of differently substituted 3-alkyl/aryl b-lactams having significant anti-microbial activities have given insight that substitution at C-3 and C-4 of b-lactam ring affects the biological activity of the ring. So, keeping this in mind and synthetic utility of b-lactams here we have made an attempt towards the feasibility and efficiency of 3-(p-substituted-phenylthio)-b-lactams towards Lewis acid functionalization reactions. In our previous works, we have explored the synthetic utility of cis-3-chloro-3-phenyl/benzyl/methylthio-b-lactams as suitable substrate for the Lewis acid catalysed nucleophilic substitution. The current work is designed to explore the effect of electronic changes at phenylthio group at C-3 on the products profile in the Lewis acid catalysed nucleophilic substitution reactions.