Biogenetic-type synthesis of penicillin-cephalosporin antibiotics. I. Stereocontrolled synthesis of the penam- and cephem-ring systems from an acyclic tripeptide equivalent

Application of the N-Dibenzyl Protective Group in the Preparation of β-Lactam Pseudopeptides

“…Next, each of the three compounds 1a – 1c was treated under different reaction conditions. The idea was also to avoid high reaction temperatures and strong bases, such as lithium diisopropylamide (LDA) or NaH, which have otherwise been used in other β-lactam ring preparations [11,21]. Firstly, the conversion of an alcoholic OH group of serine to a sulfonate group was tested because it is widely used in aziridine ring formation, in which carbamate or trityl nitrogen is used as the nitrogen source [22,23].…”

Bulky α,β-dehydroamino acids: their occurrence in nature, synthesis, and applications

“…In 1975, Kishi and co-workers synthesized DVal-containing peptide 47 via elimination of the dipeptide derived from coupling of amino acid 45 with penicillamine methyl ester (46, Scheme 1). 101 This route was inspired by the proposed biosynthetic pathway to the penicillins and cephalosporins. In related work that also targeted these antibiotics, the DVal moiety of b-lactam thiazolidine 49 was generated via treatment of 48 with aluminum amalgam (Scheme 2).…”

Naturally Occurring β-Lactams

“…Reduction and Schiffs base formation gives (226) which can be converted to (± )-cephalothin. On the other hand introduction of the thiomethyl group followed by acylation gives (227), ideally suited for conversion to (228) and ultimately (± )-cefoxitin (200 One other approach to the cephamycin ring system is that reported by KISHI (201,202) using a synthetic scheme based mainly on biosynthetic pathways suggested by COOPER (203). N-Acetylbromodehydroalanine tbutyl ester (229) was converted to the methoxydibromo acid (230), and then to the dehydrovaline derivative (231).…”