Tandem Addition/Cyclization of Alkynylzinc Reagents to Enantiopure 2‐tert‐Butyl‐3,5‐dimethyl‐2,3‐dihydroimidazol‐4‐one N‐Oxide: Potential Precursors of Quaternary α‐Amino Acids

Abstract

A new enantiopure cyclic nitrone, a potential electrophilic alanine synthon, has been prepared. Its reaction with alkynylzinc reagents led to a tandem addition/cyclization reaction with complete regio-and stereoselectivity. The adducts are potential precursors of quaternary α-amino acids.

Omphalotins E–I, Five Oxidatively Modified Nematicidal Cyclopeptides from Omphalotus olearius

“…The chemical shifts of the N-hydroxylated aminal unit were in agreement with those reported for related structures. [5][6][7] Representative HMBC correlations are summarized in Figure 2. The longwave UV absorption maximum is hypsochromically shifted by about 10 nm in N-hydroxylated compound 2, which was also reported for N-hydroxylated anilines.…”

4‐Isoxazolines: Scaffolds for Organic Synthesis

“…Scheme 5. Treatment of the chiral cyclic nitrone 23 (Scheme 6) with alkynylzinc reagents led to a tandem addition/cyclization process giving the bicyclic 4-isoxazolines 24 regio-and diastereoselectively. [18] Although the outcome of the reaction is the expected 1,3-dipolar cycloadducts the reaction follows a two-step pathway, as demonstrated by the authors by TLC analysis of hydrolysed aliquots of the reaction mixture, showing the formation and disappearance of the intermediate 23.…”

The chemistry of 2,3-dihydroisoxazole derivatives

“…Reactions of intermediates 10 with DCl in D 2 O or with N iodosuccinimide give deuterated or iodo prod ucts, respectively. 24 It is worth noting that the enantio meric purity of products 11 is high (ee = 80-93%).…”