Nuclear analogs of .beta.-lactam antibiotics. 2. The total synthesis of 8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acids

Chromogenic depsipeptide substrates for β-lactamases and penicillin-sensitive dd-peptidases

“…HMDSO ([2H]chloroform) 1.6 (s, 9H), 4.3 (d, 2H), 4.7 (s, 2H), 7.15 (s, broad, 1 H) and 7.3-8 (m, 5 H). The acid function was deprotected as described by Bryan et al (1977). The final white crystalline powder (m.p.…”

Novel synthesis of 3,4-dihydro-5-bromo[1,4]oxazin-2-one derivatives, new protease inhibitor scaffold

“…Upon treatment with TFA in CH 2 Cl 2 , tert-butyl esters 3a-c and 4a-c were easily deprotected into the corresponding carboxylic acids 5a-c and 6a-c in quantitative yields. 11 The key step of this synthesis was the cyclisation of carboxylic acid 5a-c and 6a-c into the corresponding 3,4-dihydro [1,4]oxazin-2-one core. For this purpose, we have investigated different cyclisation procedures using various chemical reagents.…”

Synthesis of Monocyclic and Bicyclic Imino Sugars

“…The imino sugar 14 was accessible by reduction of the tert ‐butyl ester with LiAlH 4 , deprotection of the tosyl amide by titration with sodium naphthalide solution19 and cleavage of the benzyl ethers with H 2 /Pd/C 17. The unnatural amino acid 16 could be obtained after removal of the tosyl protecting group and acidic cleavage of the tert ‐butyl ester in trifluoroacetic acid (TFA) 20. The resulting salt was dissolved in THF and the Bn groups were removed under conditions identical to those above.…”