Diastereo- and Enantioselective Synthesis of Orthogonally Protected 2,4-Diaminocyclopentanecarboxylates:  A Flip from β-Amino- to β,γ-Diaminocarboxylates

Abstract

Conformationally restricted, orthogonally protected 2,4-diaminocarboxylates with a cyclopentane skeleton were efficiently synthesized from beta-lactam 6, the syntheses involving strategies of diastereoselective epoxidation of the beta-lactam and the corresponding monoprotected amino esters with opposite selectivities followed by regioselective opening of the oxirane ring with sodium azide. The enantiomers were also prepared. This new class of compounds can be regarded not only as conformationally constrained beta,gamma-diamino acid derivatives but also as potential functionalized carbocyclic nucleoside precursors.

Fluorination of some functionalized cycloalkenes through epoxidation and oxirane opening with Deoxofluor or XtalFluor-E

“…In this product, the carbamate group and oxirane ring have the same steric arrangement relative to the six-membered ring. The stereoslectivity of this reaction may be attributed to the hydrogen-bonding directing effect in the transition state of the oxidation [27,28]. Surprisingly, fluorination of (±)-9 with XtalFluor-E did not afford any identifiable product.…”

Synthesis of Carbocyclic and Heterocyclic β-Aminocarboxylic Acids

“…Three useful epoxy β-amino ester stereoisomer intermediates (307− 309) for this purpose were prepared from 2-aminocyclopentenecarboxylic acid or from a cyclopentadiene-derived bicyclic β-lactam by means of epoxidation based on opposite selectivities (Figure 18). 80 These epoxy amino esters were then subjected to azidolysis with NaN 3 , resulting regioselectively in the corresponding 4-azido-substituted β-amino esters 310−313 (Figure 19). 80 These compounds can be regarded as orthogonally protected β,γ-diaminocarboxylic acid derivatives.…”

“…80 These epoxy amino esters were then subjected to azidolysis with NaN 3 , resulting regioselectively in the corresponding 4-azido-substituted β-amino esters 310−313 (Figure 19). 80 These compounds can be regarded as orthogonally protected β,γ-diaminocarboxylic acid derivatives.…”

“…80 An optically active 1,2,3-triazole-substituted cispentacin derivative was synthetized when azido amino ester enantiomer 310 was reacted with symmetrical diethyl acetylenedicarboxylate through an azide−alkyne 1,3-dipolar cycloaddition. The reaction took place readily in refluxing EtOH to give enantiopure 314 (Scheme 62).…”

Selective functionalization of alicyclic beta-amino acids by 1,3-dipolar cycloaddition of nitrile oxides

“…NaOMe or NaOEt). [33][34][35][36][37][38][39][40][41][42]106 The isomerization in the presence of a base is an equilibrium process, which the equilibrium is shifted towards the thermodynamically stable trans ester.…”