Studies on the constituents of Broussonetia species VIII. Four new pyrrolidine alkaloids, broussonetines R, S, T, and V and a new pyrroline alkaloid, broussonetine U, from Broussonetia kazinoki Sieb

Four new pyrrolidine alkaloids, broussonetines R, S, T, and V and a new pyrroline alkaloid, broussonetine U were isolated from the branches of Broussonetia kazinoki SIEB. (Moraceae) in low yield. Broussonetines R, S and T were formulated as (2R,3R,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-[(1R)-1-hydroxy-3-[6-(4-hydroxybutyl)-cyclohexy-2-on-1(6)-enyllpropyl] pyrrolidine (1), (2R,3R,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-[(1R,10S)-1,10,13-trihydroxytridecyl] pyrrolidine (2), (2R,3R,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-[(1R,5S)-1,5, 13-trihydroxy-10-oxo-tridecyl] pyrrolidine (3). And broussonetines U and V were proposed to be (2S,3S,4S)-2-hydroxymethyl-3, 4-dihydroxy-5-(9-oxo-13-hydroxytridecyl)-5-pyrroline (4), (2R,3S,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-[(E)-9-oxo-13-hydroxy-3-tridecenyl] pyrrolidine (5), respectively, by spectroscopic and chemical methods.     

Studies on the constituents of Broussonetia species X. Six new alkaloids from Broussonetia kazinoki Sieb.

Six new alkaloids, broussonetines W, X, M1, U1, J3, and J2 (1-6) were isolated from the branches of Broussonetia kazinoki SIEB. (Moraceae) as minor constituents. They were formulated as (2R,3R,4R,5R)-2-hydroxy-methyl-3,4-dihydroxy-5-17-(cyclohexy-2-on-1(6)-enyl)heptyllpyrrolidine (1), (2R,3S,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-17-(cyclohexy-2-on-1(6)-enyl)heptyl]pyrrolidine-4-O-beta-D-glucopyranoside (2), (2R,3R,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-[(9R)-9,13-dihydroxytridecyl]- pyrrolidine (3), (2S,3S,4S)-2-hydroxymethyl-3,4-dihydroxy-5-(10-oxo-13-hydroxytridecyl)-5- pyrroline (4), (2R)-2-[(IS,2S)-1,2-dihydroxy-8-1(2R,3R,4R,5R)-5-(2-hydroxymethyl-3,4-dihydroxy-1-acetylpyrrolidinyl)loctyl]piperidine (5), (2R)-2-[(1S,2S)-1,2-dihydroxy-8-[(2R,3R, 4R,5R)-5-(2-hydroxymethy]-3,4-dihydroxypyrrolidinyl)]octyl]piperidine (6).     

Three new sesquiterpenoid glucosides of Ficus pumila fruit

As the glycosyl constituents of Ficus pumila L. fruits (Moraceae), three new sesquiterpenoid glucosides, pumilasides A, B and C were isolated together with benzyl beta-D-glucopyranoside, (E)-2-methyl-2-butenyl beta-D-glucopyranoside and rutin. Their structures were characterized as (1S,4S,5R,6R,7S,10S)-1,4,6-trihydroxyeudesmane 6-O-beta-D-glucopyranoside, (1S,4S,5S,6R,7R,10S)-1,4-dihydroxymaaliane 1-O-beta-D-glucopyranoside and 10 alpha, 11-dihydroxycadin-4-ene 11-O-beta-D-glucopyranoside by spectral and chemical methods.     

Five new nortropane alkaloids and six new amino acids from the fruit of Morus alba LINNE growing in Turkey

Investigation of the constituents of the fruits of Morus alba LINNE (Moraceae) afforded five new nortropane alkaloids (1-5) along with nor-psi-tropine (6) and six new amino acids, morusimic acids A-F (7-12). The structures of the new compounds were determined to be 2alpha,3beta-dihydroxynortropane (1), 2beta,3beta-dihydroxynortropane (2), 2alpha,3beta,6exo-trihydroxynortropane (3), 2alpha,3beta,4alpha-rihydroxynortropane (4), 3beta,6exo-dihydroxynortropane (5), (3R)-3-hydroxy-12-[(1S,4S)-4-[(1S)-1-hydroxyethyl]-pyrrolidin-1-yll-dodecanoic acid-3-O-beta-D-glucopyranoside (7), (3R)-3-hydroxy-12-[(1S,4S)-4-[(1S)-1-hydroxyethyl]-pyrrolidin-1-yll-dodecanoic acid (8), (3R)-3-hydroxy-12-1(1R,4R,5S)-4-hydroxy-5-methyl-piperidin-1-yll-dodecanoic acid-3-O-beta-D-glucopyranoside (9), (3R)-3-hydroxy-12-[(1R,4R,5S)-4-hydroxy-5-methyl-piperidin-1-yll-dodecanoic acid (10), (3R)-3-hydroxy-12-[(1R,4R,5S)-4-hydroxy-5-hydroxymethyl-piperidin-1-yl]-dodecanoic acid-3-O-beta-D-glucopyranoside (11), and (3R)-3-hydroxy-12-[(1R,4S,5S)-4-hydroxy-5-methyl-piperidin-1-yl]-dodecanoic acid (12) on the basis of spectral and chemical data.     

Two new bioactive sesquiterpenes from the soft coral Sinularia sp

Two new sesquiterpenes, 1S*, 4R*, 5S*, 6R*, 7S*, 10S*-1(5), 6(7)-diepoxy-4-guaiol (1) and 1S*, 4S*, 5S*, 10R*-4,10-guaianediol (2) have been isolated from the ethyl acetate soluble portion of the soft coral Sinularia sp., and their stereostructure were determined by spectroscopic methods and by X-ray single crystal analysis. Both compounds showed antioxidant and cytotoxic activities.     

Structures of new sesquiterpenoids from Farfarae Flos

Two new bisabolane-type sesquiterpenoids, (3R,4R,6S)-3,4-epoxybisabola-7(14),10-dien-2-one and (1R,3R,4R,5S,6S)-1-acetoxy-8-angeloyloxy-3,4-epoxy-5-hydroxybisabola-7(14),10-dien-2-one, and a new oplopane-type sesquiterpenoid, 14(R)-hydroxy-7beta-isovaleroyloxyoplop-8(10)-en-2-one, were isolated from Farfarae Flos along with three known compounds. The structures of these compounds were elucidated on the basis of spectroscopic evidence.     

Isofagomine lactams,synthesis and enzyme inhibition

The synthesis of isofagomine lactams (2-oxoisofagomines) corresponding to the biologically important hexoses is presented. The D-glucose/D-mannose analogue (3S,4R,5R)-3,4-dihydroxy-5-hydroxymethylpiperidin-2-one (9) was synthesised in 9 steps from D-arabinose, the D-galactose analogue (3S,4S,5R)-3,4-dihydroxy-5-hydroxymethylpiperidin-2-one (10) was synthesised in 11 steps from D-arabinose and the L-fucose analogue (3R,4R,5R)-3,4-dihydroxy-5-methylpiperidin-2-one (11) was synthesised in 12 steps from L-arabinose. The three lactams 9-11 were found to be glycosidase inhibitors with micro- to nanomolar inhibition constants. The lactam 10 showed slow onset inhibition of beta-galactosidase from A. Oryzae. The rate constants for this process were determined to be k(on) = 2.55 x 10(4) M-1 s-1 and k(off) = 1.7 x 10(-3) s-1. The activation energies and standard thermodynamic functions were also determined.     

Two new eremophilanolides from Xanthium sibiricum

Two new eremophilanolides, sibiriolides A (1) and B (2), were isolated from the aerial parts of Xanthium sibiricum. The structures of the new compounds were identified as 4S,5R,7R,8R, 11R-2-oxo-1(10)-eremophilen-12,8-olide (1) and 4S,5R,7R,8R,11S-2-oxo-1(10)-eremophilen-12,8-olide (2) by HREIMS and NMR spectroscopic techniques in combination with X-ray crystallographic analysis and CD measurements.     

Studies on the constituents of Broussonetia species. VII. Four new pyrrolidine alkaloids, broussonetines M, O, P, and Q, as inhibitors of glycosidase, from Broussonetia kazinoki SIEB

Four new pyrrolidine alkaloids, broussonetines M, O, P, and Q, were isolated from the branches of Broussonetia kazinoki SIEB, (Moraceae). Broussonetines M, O, P, and Q were formulated as (2R,3R,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-[(10S)-10,13-dihydroxy-tri decyl]pyrrolidine (1), (2R,3R,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-[(E)9-oxo-13-hydroxy-3- tridecenyl]pyrrolidine (2), (2R,3R,4R,5R)-2-hydroxymethyl-3,4-dihydroxy-5-[(E)10-oxo-13-hydroxy-3-++ +tridecenyl]pyrrolidine (3), and (2R,3S,4R,5R)-2-hydroxymethyl-3-hydroxy-4-(beta-D-glucopyranosyloxy++ +)-5-[10-oxo-13-(beta-D-glucopyranosyloxy)tridecyl]pyrrolidine (4) respectively, by spectroscopic and chemical methods. 1-4 inhibited beta-glucosidase, beta-galactosidase and beta-mannosidase.     

New calamenene sesquiterpenes from Tarenna madagascariensis

Four calamenene sequiterpenes, (+)-(7R,10S)-15-hydroxycalamenene (3), (+)-(7R,10S)-2,15-dihydroxycalamenene (4), (+)-(7R,10S)-2-hydroxy-15-calamenal (5), (+)-(7R,10S)-15-calamenal (6), along with the amorphane sesquiterpene (+)-(1S,6R,7R,10S)-1-hydroxy-3-oxo-amorph-4-ene (16), have been isolated from the Madagascan shrub Tarenna madagascariensis (Rubiaceae) and their structures determined by spectroscopic methods and chemical correlations. Furthermore, five known related sesquiterpenes [(+)-(7R,10S)-2-hydroxycalamenene (1), (+)-(7R,10S)-3-hydroxycalamenene (2), (-)-alpha-cadinol (13), cadinenal (14), 6-epicadinenal (15)], and three known lignans [(-)-hinokinin, (-)-dihydrocubebin, (-)-cubebin] were also isolated from the same plant. This is the first report of compounds 3, 4, 5, 6, and 16 from a natural source.     

Glycosides of Atractylodes lancea

Five sesquiterpenoid glycosides (two guaiane-type glycosides and three eudesmane-type glucosides) and a glucoside of an acetylene derivative were newly isolated from the water-soluble portion of the methanolic extract of Atractylodes lancea rhizome together with 26 known compounds. Their structures were characterized as atractyloside A 14-O-beta-D-fructofuranoside, (1S,4S,5S,7R,10S)-10,11,14-trihydroxyguai-3-one 11-O-beta-D-glucopyranoside, (5R,7R,10S)-isopterocarpolone beta-D-glucopyranoside, cis-atractyloside I, (2R,3R,5R,7R,10S)-atractyloside G 2-O-beta-D-glucopyranoside, and (2E,8E)-2,8-decadiene-4,6-diyne-1,10-diol 1-O-beta-D-glucopyranoside on the basis of chemical and spectroscopic investigation. The presence of six characteristic guaiane-type glucosides in both rhizomes of A. lancea and Atractylodes japonica suggested a close chemotaxonomic relationship between them.     

Synthesis and pharmacological activity of 4-amino-5-chloro-2-methoxy-N-[(2S,4S)-1-ethyl-2-hydroxymethyl-4- pyrrolidinyl]benzamide (TKS159) and its optical isomers

Of 4-amino-5-chloro-2-methoxy-N-(1-ethyl-2-hydroxymethyl-4- pyrrolidinyl)benzamide, four optical isomers, (2S,4S)-1 (TKS159), (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27, were prepared from optically active 4-amino-1-ethyl-2-hydroxymethylpyrrolidine di-p-toluenesulfonate [(2S,4S)-14, (2S,4R)-17, (2R,4S)-20 and (2R,4R)-23, respectively]. The requisites, (2S,4S)-14, (2S,4R)-17, (2R,4S)-20 and (2R,4R)-23, were prepared from a commercially available trans-4-hydroxy-L-proline. The absolute configurations of (2S,4S)-1 (TKS159), (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27 were spectroscopically determined. Of the benzamide derivatives, four optical isomers, (2S,4S)-1, (2S,4R)-25, (2R,4S)-26 and (2R,4R)-27, showed a relatively potent affinity for 5-hydroxytryptamine 4 (5-HT4) receptors in a radioligand binding assay ([3H]GR113808). The activities of 25-27 were less effective than that of 1 for the gastric emptying of a phenol red semisolid meal in rats. All this suggests that the most potent of the isomers was 4-amino-5-chloro-2-methoxy-N-[(2S,4S)-1-ethyl-2- hydroxymethyl-4-pyrrolidinyl]benzamide (1).     

Studies on the Syntheses of the Side Chains of Brassinolide and Dolicholide

(4R,5S)-2,2-Dimethyl-4-(1',2'-dimethylpropyl)-5-(1'-bromoethyl)--1,3-dioxolane(15) with the side chain of brassinolide and (4R, 5S)--2, 2-dimethyl-4-(l'-methylene-2'-methylpropyl)-5-(1'-bromoethyl) 1,3-dioxolane(14) with the side chain of dolicholide were first synthesized through 11 and 10 stepes from D-mannitol respectively. All of the intermediates 7-13 were first synthesized too.     

Conformationally constrained dipeptide surrogates with aromatic side-chains: synthesis of 4-aryl indolizidin-9-one amino acids by conjugate addition to a common alpha,omega-diaminoazelate enone intermediate

Four methyl 9-oxo-8-(N-(Boc)-amino)-4-phenyl-1-azabicyclo[4.3.0]nonane carboxylates (11, 4-Ph-I(9)aa-OMe) were synthesized from (2S,8S,5E)-di-tert-butyl-4-oxo-5-ene-2,8-bis[N-(PhF)amino]azelate [(5E)-7, PhF = 9-(9-phenylfluorenyl)] via a seven-step process featuring a conjugate addition/reductive amination/lactam cyclization sequence. Various nucleophiles were used in the conjugate addition reactions on enone (5E)-7 as a general route for making alpha,omega-diaminoazelates possessing different substituents in good yield albeit low diastereoselectivity except in the case of aryl Grignard reagents (9/1 to 15/1 drs). 6-Phenylazelates (6S)-8d and (6R)-8d were separated by chromatography and diastereoselective precipitation and independently transformed into 4-Ph-I(9)aa-OMe. From (6S)-8d, (2S,4R,6R,8S)-4-Ph-I(9)aa-OMe 11 was prepared selectively in 51% yield. Reductive amination of (6R)-8d provided the desired pipecolates 9 along with desamino compound 10, which was minimized by performing the hydrogenation in the presence of ammonium acetate. Subsequent ester exchange, lactam cyclization, and amine protection provided three products (2R,4S,6S,8R)-, (2R,4S,6S,8S)-, and (2S,4S,6R,8S)-4-Ph-I(9)aa-OMe 11 in 10, 6, and 6% yields, respectively, from (6R)-8d. Ester hydrolysis of (2S,4R,6R,8S)-11 furnished 4-phenyl indolizidin-9-one N-(Boc)amino acid 3 as a novel constrained Ala-Phe dipeptide surrogate for studying conformation-activity relationships of biologically active peptides.     

Chemoenzymatic synthesis of (+)-alpha-polypodatetraene and methyl (5R,10R,13R)-labda-8-en-15-oate

The reported enzymatic resolution products {acetate of (1S,4aS,8aS)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal} (8aS)-5 (>99% ee)] and [(1R,4aR,8aR)-1,2,3,4,4a,5,6,7,8,8a-decahydro-5,5,8a-trimethyl-2-oxo-trans-naphthalene-1-methanol-2-ethylene acetal (8aR)-4 (98% ee) were converted to (+)-alpha-polypodatetraene (1) and methyl (5R,10R,13R)-labda-8-en-15-oate (2), respectively. For the synthesis of (5R,10R,13R)-2, chiral isoprene congener (3S)-26 corresponding to the right part of 2 was synthesized based on the lipase-assisted resolution of (+/-)-2-methyl-3- (p-methoxyphenyl)propanol (17).     

Tandem ireland-claisen rearrangement ring-closing alkene metathesis in the construction of bicyclic beta-lactam carboxylic esters

4-Alkenyl-2-azetidinone systems were converted to the corresponding ethyl 2-?4-alkenyl-2-oxo-1-azetidinyl-4-pentenoates. In addition, 4-(2-propenyl-1-oxy)-, 4-(2-propenyl-1-thio)-, 4-?N-(2-propenyl)-(4-toluenesulfonyl)- and (3S, 4R)-4-(2-propenyl)-3-?(1R)-1-(tert-butyldimethylsilyloxy)ethyl-++ +azeti din-2-one were converted into beta-lactam dienes via sequential N-alkylation, Ireland-Claisen ester enolate rearrangement and esterification. Ring-closing metathesis using the Schrock ?(CF(3))(2)MeCO(2)Mo(=CHCMe(2)Ph)(=NC(6)H(3)-2,6-iso-Pr(2)) (1) or Grubbs Cl(2)(Cy(3)P)(2)Ru=CHPh (2) carbenes gave a series of ?5.2.0 and ?6.2.0 bicycles. Subsequent elaboration of the analogous (2R,7R, 8S)-tert-butyl 8-?(1R)-(tert-butyldimethylsilyloxy)ethyl-1-aza-9-oxobicyclo++ +?5.2. 0non-4-ene-2-carboxylate (15), via selenation and desilylation, gave (+)-(2S,7R,8S)-tert-butyl 8-?(1R)-hydroxyethyl-1-aza-9-oxobicyclo?5.2.0nona-2, 4-diene-2-carboxylate (18), a novel type of bicyclic beta-lactam. Diels-Alder cycloaddition further afforded tetracyclic systems exemplified by tert-butyl (1R,4S,5R,7S)-4-?(1R)-1-hydroxyethyl-3,9, 11-trioxo-10-phenyl-2,8,10,12-tetraazatetracyclo?5.5.2.0.(2, 5)0(8, 12)tetradec-13-ene-1-carboxylate (19).     

Simiranes A and B: erythroxylanes diterpenes and other compounds from Simira eliezeriana (Rubiaceae)

The first phytochemical study of Simira eliezeriana Peixoto (Rubiaceae) allowed the isolation and structural determination of two new diterpenes named simirane A [(5R,6R,8R,9R,10S,11S,13S)-6β,11β-dihydroxy-2,4(18),15-erythroxylatrien-1-one] (1) and simirane B [(5S,8R,9R,10S,11S,13S)-11β-hydroxy-2,4(18),15-erythroxylatrien-1-one] (2), together with seven known compounds: sitosterol (3), stigmasterol (4), campesterol (5), coniferaldehyde (6), vanillin (7), pinoresinol (8) and harman (9) from the bark of the plant. The structures of the compounds were established on the basis of spectroscopic methods, including 1-D and 2-D NMR, HRESI-MS and CD analysis and comparisons with available literature data of known compounds.     

Synthesis of Enantiomerically Pure Bis(hydroxymethyl)-Branched Cyclohexenyl and Cyclohexyl Purines as Potential Inhibitors of HIV

The synthesis of the enantiomerically pure bis(hydroxymethyl)-branched cyclohexenyl and cyclohexyl purines is described. Racemic trans-4,5-bis(methoxycarbonyl)cyclohexene [(+/-)-6] was reduced with lithium aluminum hydride to give the racemic diol (+/-)-7. Resolution of (+/-)-7 via a transesterification process using lipase from Pseudomonas sp. (SAM-II) gave both diols in enantiomerically pure form. The enantiomerically pure diol (S,S)-7was benzoylated and epoxidized to give the epoxide 9. Treatment of the epoxide 9 with trimethylsilyl trifluoromethanesulfonate and 1,5-diazabicyclo[5.4.0]undec-5-ene followed by dilute hydrochloric acid gave (1R,4S,5R)-4,5-bis[(benzoyloxy)methyl]-1-hydroxycyclohex-2-ene (10). Acetylation of 10 gave (1R,4S,5R)-1-acetoxy-4,5-bis[(benzoyloxy)methyl]cyclohex-2-ene (11). (1R,4S,5R)-1-Acetoxy-4,5-bis[(benzoyloxy)methyl]cyclohex-2-ene (11) was converted to the adenine derivative 12 and guanine derivative 13 via palladium(0)-catalyzed coupling with adenine and 2-amino-6-chloropurine, respectively. Hydrogenation of 12 and 13 gave the correspondning saturated adenine derivative 14 and guanine derivative 15. (1R,4S,5R)-4,5-Bis[(benzoyloxy)methyl]-1-hydroxycyclohex-2-ene (10) was converted to the adenine derivative 16 and guanine derivative 17 via coupling with 6-chloropurine and 2-amino-6-chloropurine, respectively, using a modified Mitsunobu procedure. Hydrogenation of 16 and 17 gave the corresponding saturated adenine derivative 18 and guanine derivative 19. Compounds 12-19 were evaluated for activity against human immunodeficiency virus (HIV), but were found to be inactive. Further biological testings are underway.     

Conformational studies on peptides containing α,α-disubstituted α-amino acids: chiral cyclic α,α-disubstituted α-amino acid as an α-helical inducer

Four types of α,α-disubstituted amino acids {i.e., α-aminoisobutyric acid (Aib), 1-aminocyclopentanecarboxylic acid (Ac(5)c), (3S,4S)-1-amino-(3,4-dimethoxy)cyclopentanecarboxylic acid [(S,S)-Ac(5)c(dOM)] and its enantiomer (R,R)-Ac(5)c(dOM)} were introduced into l-leucine-based hexapeptides and nonapeptides. The dominant conformations of eight peptides: Cbz-(L-Leu-L-Leu-dAA)(2)-OMe [dAA = 1: Aib; 2: Ac(5)c; 3: (S,S)-Ac(5)c(dOM); 4: (R,R)-Ac(5)c(dOM)] and Boc-(L-Leu-L-Leu-dAA)(3)-OMe [dAA = 5: Aib; 6: Ac(5)c; 7: (S,S)-Ac(5)c(dOM); 8: (R,R)-Ac(5)c(dOM)], were investigated by IR, CD spectra and X-ray crystallographic analysis. The CD spectra revealed that Aib hexapeptide 1 and Ac(5)c hexapeptide 2 formed right-handed (P) 3(10)-helices, while Ac(5)c(dOM) hexapeptides 3 and 4 formed a mixture of (P) 3(10)- and α-helices. The Aib nonapeptide 5 formed a (P) 3(10)-helix, the Ac(5)c nonapeptide 6 formed a mixture of (P) 3(10)- and α-helices, and the Ac(5)c(dOM) nonapeptides 7 and 8 formed (P) α-helices. X-Ray crystallographic analysis revealed that the Aib hexapeptide 1 formed a (P) 3(10)-helix, while (S,S)-Ac(5)c(dOM) hexapeptide 3 formed a (P) α-helix. In addition, the Ac(5)c nonapeptide 6 and (R,R)-Ac(5)c(dOM) nonapeptide 8 formed (P) α-helices. The Aib and achiral Ac(5)c residues have the propensity to form 3(10)-helices in short peptides, whereas the chiral Ac(5)c(dOM) residues have a penchant for forming α-helices.     

手性双二茂铁基配体的合成、表征及固体CD光谱

以甲酰基二茂铁(1)和手性1,2-二苯基乙二胺[(1R, 2R)-1,2-二苯基乙二胺(2R), (1S,2S)-1,2-二苯基乙二胺(2S)]为原料, 经缩合、还原和N-烷基化反应, 制备了一对新型手性四齿双二茂铁基配体[N,N’-二(二茂铁基甲基)-N,N’-二(2-羟基丙基)-(1R,2R)-1,2-二苯基乙二胺(5R)和N,N’-二(二茂铁基甲基)-N,N’-二(2-羟基丙基)-(1S,2S)-1,2-二苯基乙二胺(5S)]. 用元素分析、红外(IR)、质子核磁共振(1H NMR)、紫外-可见(UV-Vis)、固体圆二色(CD)光谱等对手性产物(3R-5S)进行了表征. 固体CD光谱研究表明, 配体5R(或5S)的手性特征和4R(或4S)相似而与3R(或3S)却有一定差别.