Cycloadditions of aromatic imines to enantiomerically pure stabilized azomethine ylids: Construction of threo (2S, 3R)-3-aryl-2,3-diamino acids

The Chemistry of Vicinal Diamines

“…Treatment of propyl nitronate with (S)-PhCH(Me)NCHPh led essentially to one anti-b-nitro amine; access to homochiral 1,2-diamines by using this method may thus be envisioned. The cycloaddition of aromatic imines 451 to enantiomerically pure azomethine ylides derived from (5S)-phenylmorpholin-2-one 450, as described by Harwood et al, [199] was completely diastereoselective (Scheme 112). Hydroge- nolysis of the cycloadducts 453 under acidic conditions afforded the corresponding syn-(2S,3R)-3-aryl-2,3-diamino acids 454, which were thus prepared in a straightforward two-step sequence.…”

Morpholinone mediated oxazolone‐free C‐terminus amide coupling permitting a convergent strategy for peptide synthesis

“…Morpholinone-based chiral relay systems for the preparation of optically active amino acids have been a major research focus of our group over many years [7][8][9]. We herein report a novel approach for the convergent synthesis (N-and C-terminus extension) of peptides using these morpholinone templates as key structural motifs.…”

Synthetic Approaches to α,β‐Diamino Acids

“…Within this context, the group of Harwood reported that chiral azomethine ylides 61 generated in situ from (5S)-phenylmorpholin-2-one 59 in the presence of aromatic aldimines 60 and pyridinium p-toluenesulfonate can undergo cycloaddition with excess of imine to give imidazolidines 62 as single products. Finally, hydrogenolysis under acidic conditions released the corresponding enantiopure syn a,b-diamino acids in excellent yields 63 (Scheme 9.9) [49]. Another remarkable example of this approach is the reaction of methyl isocyanoacetate 64 with N-sulfonyl imines 16 [R ( aryl, (E)-styryl] catalyzed by transition metal complexes such as AuCl(NCc-hex) to give racemic cis-imidazolines 65 with high diastereoselectivity.…”