Unified synthesis of enantiopure β2h, β3h and β2,3-amino acids

Stereospecific Formal [3+2] Dipolar Cycloaddition of Cyclopropanes with Nitrosoarenes: An Approach to Isoxazolidines

“…It is known that decarboxylation in isoxazolidine 5-carboxylic acids readily occurs by cleavage of the N À O bond. [15] We found that a regioisomer studied herein showed a similar reactivity. Hence, mild Pd-catalyzed deallylation [16] of allyl ester 3 d provided lactone 7 in 51 % yield.…”

Stereospecific Formal [3+2] Dipolar Cycloaddition of Cyclopropanes with Nitrosoarenes: An Approach to Isoxazolidines

“…The N ‐aryl group in 3 a was successfully cleaved under oxidative conditions14 to provide 6 in 40 % yield of isolated product. It is known that decarboxylation in isoxazolidine 5‐carboxylic acids readily occurs by cleavage of the NO bond 15. We found that a regioisomer studied herein showed a similar reactivity.…”

Asymmetric synthesis of enantiopure isoxazolidinone monomers for the synthesis of β3-oligopeptides by chemoselective amide ligation

“…The key advantage of this approach overall of the others considered is the ease of securing the cycloadducts in enantiomerically pure form 25. Cycloadditions of nitrones generated in situ from an aldehyde and the d -gulose-derived chiral auxiliary are generally cleaner, higher yielding, and more diastereoselective with cyclic acrylate 33 .…”

“…These cycloadditions with many different aldehydes and the utility of the resulting enantiomerically pure products for β 3 -amino acid synthesis are the subject of a separate publication 25. For the purpose of our studies on the incorporation of β 3 - N -hydroxyamino acids into peptides, we selected the aliphatic substituted monomers (leucine, valine, phenylalanine, and alanine) for further investigations.…”