Plasma appearance of unesterified astaxanthin geometrical E/Z and optical R/S isomers in men given single doses of a mixture of optical 3 and 3'R/S isomers of astaxanthin fatty acyl diesters

Appearance, pharmacokinetics and distribution of astaxanthin all-E-, 9Z- and 13Z-geometrical and (3R,3'R)-, (3R,3'S)- and (3S,3'S)-optical isomers in plasma fractions were studied in three middle-aged male volunteers (41-50 years) after ingestion of a single meal containing first a 10-mg dose equivalent of astaxanthin from astaxanthin diesters, followed by a dose of 100 mg astaxanthin equivalents after 4 weeks. Direct resolution of geometrical isomers and optical isomers of astaxanthin dicamphanates by HPLC after saponification showed that the astaxanthin consisted of 95.2% all-E-, 1.2% 9Z- and 3.6% 13Z-astaxanthin, of (3R,3'R)-, (3R,3'S; meso)- and (3S,3'S)-astaxanthin in a 31:49:20 ratio. The plasma astaxanthin concentration-time curves were measured during 76 h. Astaxanthin esters were not detected in plasma. Maximum levels of astaxanthin (C(max)=0.28+/-0.1 mg/l) were reached 11.5 h after administration and the plasma astaxanthin elimination half-life was 52+/-40 h. The C(max) at the low dose was 0.08 mg/l and showed that, the dose response was non-linear. The (3R,3'R)-astaxanthin optical isomer accumulated selectively in plasma compared to the (3R,3'S)- and (3S,3'S)-isomers, and comprised 54% of total astaxanthin in the blood and only 31% of total astaxanthin in the administered dose. The astaxanthin Z-isomers were absorbed selectively into plasma and comprised approximately 32% of total astaxanthin 6-7.5 h postprandially. The proportion of all-E-astaxanthin was significantly higher in the very low density lipoproteins and chylomicrons (VLDL/CM) plasma lipoprotein fraction than in the high density lipoproteins (HDL) and low denisty lipoproteins (LDL) fractions (P<0.05). The results indicate that a selective process increase the relative proportion of astaxanthin Z-isomers compared to the all-E-astaxanthin before uptake in blood and that the astaxanthin esters are hydrolyzed selectively during absorption.     

Astaxanthin from the red crab langostilla (Pleuroncodes planipes): optical R/S isomers and fatty acid moieties of astaxanthin esters

The composition of the fatty acids of astaxanthin esters and the distribution of astaxanthin optical RS isomers in the esterified and unesterified astaxanthin fractions extracted from the meal of the pelagic red crab langostilla (Pleuroncodes planipes; Decapoda, Anomura) were determined. Astaxanthin diesters comprised approximately 70%, monoesterified astaxanthin approximately 12%, and unesterified astaxanthin approximately 10% of total carotenoids, respectively. Unidentified carotenes and minor yellow xanthophylls represented approximately 8% of the total carotenoids. Three astaxanthin diester fractions (ratio 5:4:1) and one monoester fraction were clearly distinguished by thin-layer chromatography, and fatty acid moieties were determined in all of them. Saturated fatty acids accumulated in astaxanthin diesters, but were reduced in the monoester fraction when compared to langostilla crude oil extract (CE). Astaxanthin diesters, but not monoesters were enriched in C16:0 and C18:1n-9, when compared to the CE. Astaxanthin monoesters were rich in polyunsaturated fatty acids (approximately 70% of total fatty acids), in particular C20:5n-3 and C22:6n-3. Acylation of astaxanthin in langostilla seems to be selective rather than specific. The three diesterified astaxanthin fractions of langostilla had a ratio of approximately 3:1:3 between the (3R,3'R)-, (3R,3'S)-, and (3S,3'S)-astaxanthin isomers, whereas in the monoesterified and unesterified fractions the ratio was approximately 4:1:4. The astaxanthin optical RS isomer composition indicates that langostilla is unable to racemize astaxanthin.     

The first isolation of enantiomeric and meso-zeaxanthin in nature

Racemic mixtures of (3RS, 3'RS)-zeaxanthin were separated into the three optical isomers, (3R, 3'R)-zeaxanthin (1), (3R,3'S;meso)-zeaxanthin (2) and (3S,3'S)-zeaxanthin (3), by converting to their corresponding dibenzoates and by using HPLC on an optical resolution column Sumipax OA-2000. According to this procedure, it has been shown that only (1) is isolated from higher plants, shellfish, starfish, sea squirt, sea cucumber and then examined; on the other hand (1), (2) and (3) are isolated from zeaxanthin fraction of shrimp, fish and turtle examined. This is the first isolation of enantiomeric and meso-zeaxanthin in nature.     

Partial synthesis of serum carotenoids and their metabolites

Human serum and tissues contain in excess of 12 dietary carotenoids and several metabolites that originate from consumption of fruits and vegetables. Among these are hydroxycarotenoids: (3R,3'R,6'R)-lutein (1), (3R,3'R)-zeaxanthin (2), (3R,6'R)-α-cryptoxanthin (3), and (3R)-β-cryptoxanthin (4). In addition, several dehydration products of 1 have also been identified in human serum, these are: (3R,6'R)-3-hydroxy-3',4'-didehydro-β,γ-carotene (5), (3R,6'R)-3-hydroxy-2',3'-didehydro-β,ε-carotene (6), and (3R)-3-hydroxy-3',4'-didehydro-β,β-carotene (7). Several metabolites of 1 and/or 2, namely, (3R,3'S,6'R)-lutein (3'-epilutein, 8) and (3R,3'S;meso)-zeaxanthin (9) have also been characterized in human serum and ocular tissues. Semi-synthetic processes have been developed that separately transform commercially available 1 into 4 via 7 as well as 1 into 8. While 8 is converted into 2 by base-catalyzed isomerization, 7 is transformed into 2 and its (3R,3'S;meso)-stereoisomer (9) by regioselective hydroboration.     

Astaxanthin and its metabolites idoxanthin and crustaxanthin in flesh, skin, and gonads of sexually immature and maturing Arctic charr (Salvelinus alpinus (L.))

Carotenoid compositions of the flesh, skin, and ovaries were determined in sexually maturing and immature Arctic charr (Salvelinus alpinus) fed diets supplemented with astaxanthin (optical isomer ratio (3S,3'S):(3R,3'S; meso):(3R,3'R); 1:2:1). Astaxanthin comprised 64-79% of the flesh carotenoids, and the 3',4'-cis and 3',4'-trans glycolic isomers of idoxanthin, present in a 1:1 ratio, represented 20-35%. The flesh of the sexually maturing charr contained relatively more idoxanthin than that of sexually immature fish (20 vs 35% of total carotenoids), possibly being indicative of a higher metabolic turnover of astaxanthin in the latter. The relative proportions of flesh carotenoids were unaffected by sex. The relative carotenoid composition of ovaries was similar in sexually maturing and immature females. The 3',4'-cis and 3',4'-trans glycolic isomers of idoxanthin (ratio 0.7:1) were the major carotenoids (56% of total), followed by crustaxanthin (20%), and astaxanthin comprised less than 5% of ovarian carotenoids. Three glycolic isomers of crustaxanthin were detected (3,4,3',4'-di-cis-:3,4-cis-3',4'-trans-:3,4,3',4'-di-trans-glycolic isomer ratio 2.6:3.1:1) in the ovaries. Sex and maturity status had no apparent effect on the relative composition of skin carotenoids. The skin carotenoids consisted mainly of diesters (82-87% of total carotenoids) and monoesters (7-13% of total carotenoids). Saponification revealed that astaxanthin comprised 85% and idoxanthin 10% of total carotenoids, and minor amounts of tunaxanthin-, lutein-, and zeaxanthin-like metabolites were also present. Maturity status seems to be more important than sex in determining the relative carotenoid composition of the tissues of Arctic charr, with astaxanthin and its metabolites being selectively accumulated in different tissues.     

Plasma appearance and distribution of astaxanthin E/Z and R/S isomers in plasma lipoproteins of men after single dose administration of astaxanthin

Appearance, pharmacokinetics, and distribution of astaxanthin E/Z and R/S isomers in plasma and lipoprotein fractions were studied in 3 middle-aged male volunteers (37-43 years) after ingestion of a single meal containing a 100 mg dose of astaxanthin. The astaxanthin source consisted of 74% all-E-, 9% 9Z-, 17% 13Z-astaxanthin (3R,3'R-, 3R,3'S; meso-, and 3S,3'S-astaxanthin in a 1:2:1 ratio). The plasma astaxanthin concentration--time curves were measured during 72 hr. Maximum levels of astaxanthin (1.3 +/- 0.1 mg/L) were reached 6.7 +/- 1.2 hr after administration, and the plasma astaxanthin elimination half-life was 21 +/- 11 hr. 13Z-Astaxanthin accumulated selectively, whereas the 3 and 3'R/S astaxanthin distribution was similar to that of the experimental meal. Astaxanthin was present mainly in very low-density lipoproteins containing chylomicrons (VLDL/CM; 36-64% of total astaxanthin), whereas low-density lipoprotein (LDL) and high-density lipoprotein (HDL) contained 29% and 24% of total astaxanthin, respectively. The astaxanthin isomer distribution in plasma, VLDL/CM, LDL, and HDL was not affected by time. The results indicate that a selective process increases the relative proportion of astaxanthin Z-isomers compared to the all-E-astaxanthin during blood uptake and that astaxanthin E/Z isomers have similar pharmacokinetics.     

Is (9Z)‐“meso”‐zeaxanthin optically active?

The question raised in the title was answered. (3R, 3'S)-meso-Zeaxanthin was submitted to iodine catalyzed photochemical stereoisomerisation. The enantiomeric (9Z) and (9'Z) geometrical isomers were isolated by semipreparative HPLC and separated as diastereomeric dicarbamates on a chiral column only. Cleavage of the carbamate could not be effected. CD-Spectra of (1"S, 1"S)- and (1"R, 1"R)-dicarbamates of geometrical isomers of (3R, 3'R)- and (3R, 3'S)-meso-zeaxanthin were systematically studied and the contribution from the carbamate moieties revealed. It was concluded that (9Z, 3R, 3'S)-"meso"-zeaxanthin, in spite of having no symmetry elements, is optically inactive. The result has been rationalised in line with the current hypothesis on the origin of carotenoid CD spectra.     

Rare carotenoids, (3R)-saproxanthin and (3R,2'S)-myxol, isolated from novel marine bacteria (Flavobacteriaceae) and their antioxidative activities

We isolated three orange or yellow pigment-producing marine bacteria, strains 04OKA-13-27 (MBIC08261), 04OKA-17-12 (MBIC08260), and YM6-073 (MBIC06409), off the coast of Okinawa Prefecture in Japan. These strains were classified as novel species of the family Flavobacteriaceae based on their 16S rRNA gene sequence. They were cultured, and the major carotenoids produced were purified by chromatographic methods. Their structures were determined by spectral data to be (3R)-saproxanthin (strain 04OKA-13-27), (3R,2'S)-myxol (strain YM6-073), and (3R,3'R)-zeaxanthin (strains YM6-073 and 04OKA-17-12). Saproxanthin and myxol, which are monocyclic carotenoids rarely found in nature, demonstrated significant antioxidative activities against lipid peroxidation in the rat brain homogenate model and a neuro-protective effect from L-glutamate toxicity.     

2,2'-beta-hydroxylase (CrtG) is involved in carotenogenesis of both nostoxanthin and 2-hydroxymyxol 2'-fucoside in Thermosynechococcus elongatus strain BP-1

We identified the molecular structures, including the stereochemistry, of all carotenoids in Thermosynechococcus elongatus strain BP-1. The major carotenoid was beta-carotene, and its hydroxyl derivatives of (3R)-beta-cryptoxanthin, (3R,3'R)-zeaxanthin, (2R,3R,3'R)-caloxanthin and (2R,3R,2'R,3'R)-nostoxanthin were also identified. The myxol glycosides were identified as (3R,2'S)-myxol 2'-fucoside and (2R,3R,2'S)-2-hydroxymyxol 2'-fucoside. 2-Hydroxymyxol 2'-fucoside is a novel carotenoid, and similar carotenoids of 4-hydroxymyxol glycosides were previously named aphanizophyll. Ketocarotenoids, such as echinenone and 4-ketomyxol, which are unique carotenoids in cyanobacteria, were absent, and genes coding for both beta-carotene ketolases, crtO and crtW, were absent in the genome. From a homology search, the Tlr1917 amino acid sequence was found to be 41% identical to 2,2'- beta-hydroxylase (CrtG) from Brevundimonas sp. SD212, which produces nostoxanthin from zeaxanthin. In the crtG disruptant mutant, 2-hydroxymyxol 2'-fucoside, caloxanthin and nostoxanthin were absent, and the levels of both myxol 2'-fucoside and zeaxanthin were higher. Therefore, the gene has a CrtG function for both myxol to 2-hydroxymyxol and zeaxanthin to nostoxanthin. This is the first functional identification of CrtG in cyanobacteria. We also investigated the distribution of crtG-like genes, and 2-hydroxymyxol and/or nostoxanthin, in cyanobacteria. Based on the identification of the carotenoids and the completion of the entire nucleotide sequence of the genome in T. elongatus, we propose a biosynthetic pathway of the carotenoids and the corresponding genes and enzymes.     

Carotenoids with a 5,6-dihydro-5,6-dihydroxy-beta-end group, from yellow sweet potato "Benimasari", Ipomoea batatas Lam

A series of carotenoids with a 5,6-dihydro-5,6-dihydroxy-beta-end group, named ipomoeaxanthins A (1), B (2), C1 (3) and C2 (4) were isolated from the flesh of yellow sweet potato "Benimasari", Ipomoea batatas Lam. Their structures were determined to be (5R,6S,3'R)-5,6-dihydro-beta,beta-carotene-5,6,3'-triol (1), (5R,6S,5'R,6'S)-5,6,5',6'-tetrahydro-beta,beta-carotene-5,6,5'6'-tetrol (2), (5R,6S,5'R,8'R)-5',8'-epoxy-5,6,5',8'-tetrahydro-beta,beta-carotene-5,6-diol (3), and (5R,6S,5'R,8'S)-5',8'-epoxy-5,6,5',8'-tetrahydro-beta,beta-carotene-5,6-diol (4) by UV-Vis, NMR, MS and CD data.     

Myxoxanthophyll in Synechocystis sp. PCC 6803 is myxol 2'-dimethyl-fucoside, (3R,2'S)-myxol 2'-(2,4-di-O-methyl-alpha-L-fucoside), not rhamnoside

We identified the molecular structures of the carotenoids in Synechocystis sp. PCC 6803. Myxoxanthophyll in this cyanobacterium was myxol 2'-dimethyl-fucoside, (3R,2'S)-myxol 2'-(2,4-di-O-methyl-alpha-L-fucoside). The sugar moiety of the pigment was not rhamnose but dimethylated fucose, which has not been reported in carotenoid glycosides. The other carotenoids were beta-carotene, (3R,3'R)-zeaxanthin, echinenone, (3'R)-3'-hydroxyechinenone and deoxymyxol 2'-dimethyl-fucoside, (2'S)-deoxymyxol 2'-(2,4-di-O-methyl-alpha-L-fucoside). Generally, the group of polar carotenoids in cyanobacteria is referred to as myxoxanthophyll, and the structure is considered to be myxol 2'-rhamnoside. Since the name myxoxanthophyll can not specify the sugar moiety and the identification of the sugar moiety is unfeasible in many cyanobacteria, we propose the following naming convention: when the sugar moiety is unknown, the name is myxol glycoside, when known, as in the case of rhamnose and alpha-L-fucose, they should be named myxol 2'-rhamnoside and myxol 2'-alpha-L-fucoside, respectively.     

Apparent digestibility coefficients and accumulation of astaxanthin E/Z isomers in Atlantic salmon (Salmo salar L.) and Atlantic halibut (Hippoglossus hippoglossus L.)

Apparent astaxanthin (3,3'-dihydroxy-beta,beta-carotene-4,4'-dione) digestibility coefficients (ADC) and carotenoid compositions of the muscle, liver, whole kidney and plasma were compared in Atlantic salmon (Salmo salar) and Atlantic halibut (Hippoglossus hippoglossus) fed a diet supplemented with 66 mg astaxanthin kg(-1) dry matter for 112 days. The astaxanthin source consisted of 75% all-E-, 3% 9Z- and 22% 13Z-astaxanthin, of (3R,3'R)-, (3R,3'S; meso)-, and (3S,3'S)-astaxanthin in a 1:2:1 ratio. The ADC of astaxanthin was significantly higher in Atlantic halibut than in Atlantic salmon after 56 and 112 days of feeding (P < 0.05). The ADC of all-E-astaxanthin was significantly higher than ADC of 9Z-astaxanthin (P < 0.05). Considerably more carotenoids were present in all plasma and tissue samples of salmon than in halibut. Retention of astaxanthin in salmon muscle was 3.9% in salmon and 0 in halibut. All-E-astaxanthin accumulated selectively in the muscle of salmon, and in plasma of salmon and halibut compared with diet. 13Z-astaxanthin accumulated selectively in liver and whole kidney of salmon and halibut, when compared with plasma. A reductive pathway for astaxanthin metabolism in halibut similar to that of salmon was shown by the presence of 3',4'-cis and trans glycolic isomers of idoxanthin (3,3',4'-trihydroxy-beta,beta-carotene-4'-one) in plasma, liver and whole kidney. In conclusion, the higher ADC of astaxanthin in halibut than Atlantic salmon may be explained by lower feed intake in halibut, and the lower retention of astaxanthin by a higher capacity to transform astaxanthin metabolically.     

Identification and characterization of a Pi isoform of glutathione S-transferase (GSTP1) as a zeaxanthin-binding protein in the macula of the human eye

Uptake, metabolism, and stabilization of xanthophyll carotenoids in the retina are thought to be mediated by specific xanthophyll-binding proteins (XBPs). A membrane-associated XBP was purified from human macula using ion-exchange chromatography followed by gel-exclusion chromatography. Two-dimensional gel electrophoresis showed a prominent spot of 23 kDa and an isoelectric point of 5.7. Using mass spectral sequencing methods and the public NCBI database, it was identified as a Pi isoform of human glutathione S-transferase (GSTP1). Dietary (3R,3'R)-zeaxanthin displayed the highest affinity with an apparent Kd of 0.33 microm, followed by (3R,3'S-meso)-zeaxanthin with an apparent Kd of 0.52 microm. (3R,3'R,6'R)-Lutein did not display any high-affinity binding to GSTP1. Other human recombinant glutathione S-transferase (GST) proteins, GSTA1 and GSTM1, exhibited only low affinity binding of xanthophylls. (3R,3'S-meso)-Zeaxanthin, an optically inactive nondietary xanthophyll carotenoid present in the human macula, exhibited a strong induced CD spectrum in association with human macular XBP that was nearly identical to the CD spectrum induced by GSTP1. Like-wise, dietary (3R,3'R)-zeaxanthin displayed alterations in its CD spectrum in association with GSTP1 and XBP. Other mammalian xanthophyll carrier proteins such as tubulin, high-density lipoprotein, low-density lipoprotein, albumin, and beta-lactoglobulin did not bind zeaxanthins with high affinity, and they failed to induce or alter xanthophyll CD spectra to any significant extent. Immunocytochemistry with an antibody to GSTP1 on human macula sections showed highest labeling in the outer and inner plexiform layers. These results indicate that GSTP1 is a specific XBP in human macula that interacts with (3R,3'S-meso)-zeaxanthin and dietary (3R,3'R)-zeaxanthin in contrast to apparently weaker interactions with (3R,3'R,6'R)-lutein.     

alpha-Glucosidase inhibitory constituents from stem bark of Terminalia superba (Combretaceae)

The CH(2)Cl(2)/CH(3)OH (1/1) extract of the dried stem bark of Terminalia superba afforded two compounds, (7S,8R,7'R,8'S)-4'-hydroxy-4-methoxy-7,7'-epoxylignan and meso-(rel 7S,8R,7'R,8'S)-4,4'-dimethoxy-7,7'-epoxylignan along with 11 known compounds. The structures of the compounds were established by analysing the spectroscopic data and also comparing it with the data of previously known analogues. All the isolated compounds were evaluated for their glycosidase inhibition activities. Gallic acid and methyl gallate showed significant alpha-glucosidase inhibition activity.     

Synthesis of highly 13C enriched carotenoids: access to carotenoids enriched with 13C at any position and combination of positions

Carotenoids and their metabolites are essential factors for the maintenance of important life processes such as photosynthesis. Animals cannot synthesize carotenoids de novo, they must obtain them via their food. In order to make intensive animal husbandry possible and maintain human and animal health synthetic nature identical carotenoids are presently commercially available at the multi-tonnes scale per year. Synthetically accessible (13)C enriched carotenoids are essential to apply isotope sensitive techniques to obtain information at the atomic level without perturbation about the role of carotenoids in photosynthesis, nutrition, vision, animal development, etc. Simple highly (13)C enriched C(1), C(2) and C(3) building blocks are commercially available via 99% (13)CO. The synthetic routes for the preparation of the (13)C enriched building blocks starting from the commercially available systems are discussed first. Then, how these building blocks are used for the synthesis of the various (13)C enriched carotenoids and apocarotenoids are reviewed next. The synthetic Schemes that resulted in (13)C enriched β-carotene, spheroidene, β-cryptoxanthin, canthaxanthin, astaxanthin, (3R,3'R)-zeaxanthin and (3R,3'R,6'R)-lutein are described. The Schemes that are reviewed can also be used to synthetically access any carotenoid and apocarotenoid in any (13)C isotopically enriched form up to the unitarily enriched form.     

Configurational analysis of cubebins and bicubebin from Aristolochia lagesiana and Aristolochia pubescens

(8S,8'R,9S)-, (8R,8'R,9R)-, and (8R,8'R,9S)-cubebins, together with (8R,8'R,8'R,8'R,9R,9'S)-bicubebin, were isolated from Aristolochia lagesiana and Aristolochia pubescens. Their structures were determined by spectroscopic methods, including 1H and 13C NMR spectroscopy at low temperatures, and by chemical transformations.     

Comparative biochemical studies of carotenoids in fishes--XXIX. Isolation of new luteins, lutein F and lutein G from marine fishes

New luteins, lutein F [(3R,3'R,6'S)-beta,epsilon-carotene-3, 3'-diol] and lutein G [(3S,3'R,6'S)-beta,epsilon-carotene-3,3'-diol] have been isolated from marine fishes.     

Study of stereoselective pharmacokinetics of anisodamine enantiomers in rabbits by capillary electrophoresis

The purpose of this study was to determine the pharmacokinetics of anisodamine enantiomers in plasma after oral and intravenous administration of racemic anisodamine in rabbits. A capillary electrophoresis method for the simultaneous separation of two pairs of enantiomers in plasma has been firstly developed and validated. Using a 75 mM phosphate buffer containing 25 mM carboxymethylated-gamma-cyclodextrin at pH 2.5, good resolution was achieved on a 45-cm uncoated fused-silica capillary at the voltage of 20 kV and 25 degrees C. The pharmacokinetics of individual anisodamine enantiomers were characterized using the CE assay, the sole method of enantiomeric separation for anisodamine. Pharmacokinetic analysis of results indicated that anisodamine enantiomers showed non-stereoselective disposition or stereoselective disposition in different rabbits. For the rabbits with non-stereoselective disposition, similar pharmacokinetic characteristics were observed between (6S, 2'S)- and (6R, 2'R)-, or (6S, 2'R)- and (6R, 2'S)-anisodamine. For the rabbits with stereoselective disposition, (6S, 2'S)- and (6R, 2'S)-anisodamine were below the established LOD, while the two remaining enantiomers also had similar pharmacokinetic profiles. Further investigations remain necessary to find out the underlying mechanism about the stereoselective disposition of (6S, 2'S)- and (6R, 2'S)-anisodamine.     

5-Hydroxy-seco-carotenoids from Pittosporum tobira

Three 5-hydroxy-seco-carotenoids were isolated from seeds of Pittosporum tobira. These structures were determined to be (3S,3'S,5'?)-3,3'-di(tetradecanoyloxy)-5'-hydroxy-5,6,5',6'-diseco-beta,beta-carotene-5,6,6'-trione (1), (3S,5?,3'S,5'R,6'S,9'Z)-3-tetradecanoyloxy-5',6'-epoxy-5,3'-dihydroxy-5',6'-dihydro-5,6-seco-beta,beta-caroten-6-one (2), and (3S,5?,3'S,5'R,6'R)-3-tetradecanoyloxy-5,3',5'-trihydroxy-6',7'-didehydro-5',6'-dihydro-5,6-seco-beta,beta-caroten-6-one (3) based on analysis of UV-vis, IR, FAB MS, and NMR spectroscopic data.     

Synthesis of epimers of L-cyclopentenylglycine using enzymatic resolution

Both epimers of the naturally occurring nonproteinogenic amino acid L-cyclopentenylglycine, (2S,1'S)- and (2S, 1'R)-2-(cyclopent-2'-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 alpha-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,1'R) isomer was obtained as a pure compound and characterized for the first time. The (2R,1'R) and (2R,1'S) isomers were obtained as N-acetyl ethyl ester derivatives.