A Contribution to the Asymmetric Synthesis of 3‐Amino β‐Lactams: The Diastereoselective [2+2] Cycloaddition Reaction of Chiral Aminoketene Equivalents with Enolizable Aldehyde‐Derived Imines

Double Insertion of Coordinated Phosphanylalkyne Ligands into a Pt−C6F5 Bond

“…[11] In other systems, the butadienyl unit invariably displays symmetric or asymmetric h 3 -allylic (through C2 ± C4) or h 1 (through C2) bonding modes. [12] When the reaction of 1 with 2 a or 3 a was monitored at room temperature no intermediates were detected. However, on the basis of preliminary experimental evidence at low -F)).…”

α-Alkyl-α-Amino-β-Lactam Peptides: Design, Synthesis, and Conformational Features

“…[10] The main reason is probably the lack of efficient methodology to generate an appropriate chiral building block. [11] Recently we reported the synthesis of the b-lactam 3 [12] (see Scheme 1), which has a removable chiral tether whose stereogenic center is close to the Ca position of the b-lactam ring. We now report that this synthetic building block acts as a new and very useful b-amino alaninate equivalent, which makes possible the preparation and study of b-lactam peptides of type 2 for the first time.…”

“…The stereochemical course of these reactions was assumed to be uniform, as established by hydrogenation of the double bond in 4 d to give 4 b, which was identical to that produced by the direct route. The R configuration at the Ca position for the major products 4 was assigned by single-crystal X-ray analysis of 4 b and 4 f. Finally, deprotection of the carbamate and azetidinone nitrogen atoms according to our procedure [12] led to the desired a-alkyl-b-aminoalanine equivalents 6 ± 8 in good overall yields.…”

Direct Synthesis of β‐N‐Glycosides by the Reductive Glycosylation of Azides with Protected and Native Carbohydrate Donors

“…Finally, the trimethylsilylmethyl substituent was cleaved by treatment with ceric ammonium nitrate in acetonitrile (90 %). [16] The benzamide 5 a was obtained without detectable erosion of the anomeric site ( 1 H NMR spectroscopic analysis). This sequence provides a complementary and highly practical alternative to the reaction of carbohydrates with ammonia, as primary N-glycosides are notoriously difficult to purify and are prone to epimerization at the anomeric position.…”