Synthesis of epimers of L‐cyclopentenylglycine using enzymatic resolution

Abstract

Both epimers of the naturally occurring nonproteinogenic amino acid L-cyclopentenylglycine, (2S,1ЈS)-and (2S,1ЈR)-2-(cyclopent-2Ј-enyl)glycine, were obtained via a procedure involving condensation of 3-chlorocyclopentene with diethyl acetylaminomalonate, deethoxycarbonylation, chromatographic separation of the resulting two pairs of enantiomers, and enzymatic resolution of the racemates employing enantioselective hydrolysis of the ethyl ester group with ␣-chymotrypsin. The method was used for preparation of 13 C-labeled compounds of interest for biosynthetic tracer experiments. Enantiomeric purity of the products was determined by chiral HPLC on a Crownpak CR(+) column. The biologically active (2S,1ЈR) isomer was obtained as a pure compound and characterized for the first time. The (2R,1ЈR) and (2R,1ЈS) isomers were obtained as N-acetyl ethyl ester derivatives.

Plant Analysis by Butterflies: Occurrence of Cyclopentenylglycines in Passifloraceae, Flacourtiaceae, and Turneraceae and Discovery of the Novel Nonproteinogenic Amino Acid 2-(3‘-Cyclopentenyl)glycine in Rinorea

“…All spectra were recorded in D 2 O at pD 6.2 ± 0.1 in order to obtain reproducible data. The epimers 9 and 10 could be distinguished on the basis of the recently described pH-dependence of their chemical shifts . Thus, the 1 H NMR analysis yielded ratios between the amino acids present, including the ratios between the epimers 9 and 10 .…”

“…The epimers 9 and 10 could be distinguished on the basis of the recently described pHdependence of their chemical shifts. 40 Thus, the 1 H NMR analysis yielded ratios between the amino acids present, including the ratios between the epimers 9 and 10. Examples of the 1 H NMR analysis are shown in Figure 2.…”

“…The resin was soaked in distilled H 2 O overnight and repeatedly washed with distilled H 2 O and EtOH, and then alternately with 2 M aqueous NaOH and 2 M aqueous HCl prior to use. Authentic 2-(2‘-cyclopentenyl)glycine (mixture of all stereoisomers) was synthesized from 3-chlorocyclopropene and diethyl 2-acetylaminomalonate similarly as previously described. ,, …”

“…Authentic 2-(2′-cyclopentenyl)glycine (mixture of all stereoisomers) was synthesized from 3-chlorocyclopropene and diethyl 2-acetylaminomalonate similarly as previously described. 18,40,46 Plant Material. Aerial parts of Passiflora citrina MacDougal (voucher DFHJJ6), P. cuneata Willd.…”