A mild and efficient approach to enantioenriched α-hydroxyethyl α,β-unsaturated δ-lactams

Abstract

A straightforward approach toward enantioenriched α-substituted α,β-unsaturated δ-lactams is described. Although a considerable number of approches toward α,β-unsaturated δ-lactams have been reported, there are relatively few examples of enantioenriched α,δ-disubstituted α,β-unsaturated δ-lactams formation. The δ-stereocenter was formed by addition of allylmagnesium bromide to an N-tert-butylsulfinyl imine. The α,β-unsaturated δ-lactam was furnished by ring-closing metathesis. Although Baylis-Hillman chemistry failed on this cyclic compound, introduction of the hydroxyethyl group prior to ring-closing metathesis was successful. A Baylis-Hillman reaction was used to introduce the substituent at the α-position of the α,β-unsaturated lactam.

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin–Anh and Chelation-Control Models

“…In the course of a synthesis of lactam derivatives, the allylation of sulfinimides was used to prepare starting materials with high optical purity (Scheme ). Other authors had performed the same reaction with the enantiomeric starting material and reported the opposite stereochemical outcome (Scheme ). It is likely that the structure of 1063 had been misassigned …”

“… Other authors had performed the same reaction with the enantiomeric starting material and reported the opposite stereochemical outcome (Scheme ). It is likely that the structure of 1063 had been misassigned …”

“…583 It is likely that the structure of 1063 had been misassigned. 582 precursors to alkaloids can also be achieved using this reaction (Scheme 439). 590,591 In both of these cases, the allyl group was used to form a six-membered ring with the homoallylic nitrogen atom by ring-closing metathesis.…”

Mimics of pramanicin derived from pyroglutamic acid and their antibacterial activity

“…Table 1: Yields for the Grignard reaction of lactam 6 giving products 7 and 8. Lactam 4 may also be selenylated and eliminated to give the unsaturated derivative 9; 33 since such a,b-unsaturated lactams 42 are quite electrophilic and suitable for a variety of nucleophilic addition processes, 43,44 and our earlier work had demonstrated efficient epoxidation of these systems, 33 an obvious question was its applicability to dihydroxylation processes, which in any case would provide a closer set of mimics to pramanicin 1. However, although an earlier examination of a closely related ester had indicated successful dihydroxylation using osmium tetroxide or potassium permanganate was possible but that product isolation was problematic, application of the ruthenium-mediated "flash dihydroxylation" procedure reported by Shing and co-workers 45 to 9…”

Synthesis of Conformationally Constrained Dipeptide Mimetics with Azabicyclo[4,3,0]nonanone and Azabicyclo[5,3,0]decanone Scaffolds

“…Bromides 9 and 10 can be prepared by bromination of the double bond in 11 and 12 and the subsequent elimination of HBr, while 11 and 12 can be easily synthesized from 13 and 14 through the RCM reaction. Since Grubbs’s group reported the synthesis of conformationally restricted amino acids and peptides using olefin metathesis, this method has been employed by several groups for the synthesis of dipeptide mimetics with azabicyclic core structures. ,,− …”