Stereocontrolled transformation of cyclohexene β-amino esters into syn- or anti-difunctionalized acyclic β2,3-amino acid derivatives

Fluorine‐Containing Functionalized Cyclopentene Scaffolds Through Ring Contraction and Deoxofluorination of Various Substituted Cyclohexenes

“…Because of the high biological relevance of β‐amino acids, we first selected as model compounds for our experiments some stereo‐ and regioisomers of cyclohexene β‐amino acids. Thus, cis ‐ and trans ‐2‐aminocyclohexenecarboxylic acids (±)‐ 1 and (±)‐ 5 were first converted by known procedures into the corresponding dihydroxylated amino esters (±)‐ 2 and (±)‐ 6 (Scheme ) …”

“…This failure, however, did not discourage us from continuing our investigation using cis ‐2‐aminocyclohex‐3‐ene carboxylic acid (±)‐ 9 , an isomer of (±)‐ 1 and (±)‐ 5 . Compound (±)‐ 9 was converted into the corresponding diol derivative (±)‐ 10 by using a literature procedure . Vicinal diol (±)‐ 10 , in turn, was subjected to NaIO 4 ‐mediated oxidative ring opening, followed by intramolecular ring closure induced by the morpholine salt.…”

“…Thus, cis-and trans-2-aminocyclohexenecarboxylic acids (±)-1 and (±)-5 were first converted by known procedures into the corresponding dihydroxylated amino esters (±)-2 and (±)-6 (Scheme 1). [5] The aldol reaction of various substituted scaffolds (e.g., amino, nitro, halogen, hydroxy, and other substituted compounds, as well as carbonyl derivatives, and some oxo esters) and its intramolecular asymmetric version [6] are well-known fundamental approaches for the formation of molecules with diverse structures containing an α, -unsaturated carbonyl moiety.…”

Stereocontrolled Synthesis of Functionalized Azaheterocycles from Carbocycles through Oxidative Ring Opening/Reductive Ring Closing Protocols

“…This method was extended and further optimized for the preparation of 7‐hydroxymethyl‐3,4,5‐trihydroxyazepane ( 76 ). The route, starting from a protected cyclohexenetriol, included only three steps: ozonolysis, reductive amination, and deprotection (Scheme ) …”

“…The ring‐closing procedure of the formed unstable diformyl intermediates (±)‐130 a , b with trifluoroethylamine and NaBH 3 CN afforded trans trifluoromethylated piperdine amino esters (±)‐131 a , b (Scheme ). Amino esters (±)‐131 a , b were accessed via an alternative pathway by epimerization at C‐4 of (±)‐128 a , b with NaOEt in EtOH with the involvement of the active methine group …”