Three 1,3,4‐trisubstituted β‐lactam antibiotics

Monobactams (2-azetidinones) are four-membered cyclic amides which exhibit very important antibacterial properties, as well as fl-lactamase- and elastaseinhibitory activities. A stereoselective asymmetric synthesis of 1,3,4-trisubstituted and 3,4-disubstituted 2azetidinones was performed using o-glucosamine as the chiral auxiliary via a Staudinger [2+2] cycloaddition. The absolute stereochemistries at C3 and C4 of three of these potential therapeutic substances: 2-[1-{(1,3dithian-2-yl)[2,2,2',2 ~-tetramethyl-4,4'-bi(1,3-dioxolanyl)-5-yl]methyl}-2-oxo-4-(E)-styrylazetidin-3-yl]isoind