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1.
Oseltamivir phosphate 1 was synthesized starting from a readily available acetonide, that is, ethyl (3R,4S,5R)-3,4-O-isopropylidene shikimate 2, through a new route via 11 steps and in 44% overall yield. The synthesis described in this article is characterized by two particular steps: the highly regioselective and stereoselective facile nucleophilic replacement of an OMs by an N3 group at the C-3 position of ethyl (3R,4S,5R)-3,4-O-bismethanesulfonyl-5-O-benzoyl shikimate 5, and the mild ring-opening of an aziridine with 3-pentanol at the C-1 position of ethyl (1S,5R,6S)-7-acetyl-5-benzoyloxy-7-azabicyclo[4,1,0]hept-2-ene-3-carboxylate 8. 相似文献
2.
Novel total syntheses of (R)-(?)-pyridindolol 1, (R)-(?)-pyridindolol K1 2, and (R)-(?)-pyridindolol K2 3 are described. By using l-tryptophan methyl ester and (S)-2,3-O-isopropylidene-l-glyceraldehyde as the starting materials, (R)-(?)-pyridindolol 1, (R)-(?)-pyridindolol K1 2, and (R)-(?)-pyridindolol K2 3 were synthesized in 5–7 steps in 66%, 41%, and 55% overall yields, respectively. The characteristic step of the total syntheses is a mild one-pot aromatization of N-tosyl-1,2,3,4-tetrahydro-β-carboline (N-Ts-THBC), which was obtained via Pictet–Spengler reaction of l-tryptophan methyl ester with (S)-2,3-O-isopropylidene-l-glyceraldehyde, and subsequent N-tosylation. 相似文献
3.
《Tetrahedron: Asymmetry》2005,16(17):2954-2958
Laterally lithiated (S)-(−)- and (R)-(+)-o-toluamides 6 with a chiral auxiliary derived from (S)- and (R)-phenylalaninol, respectively, were used as the building blocks and chirality inductors in the asymmetric modification of the Pomeranz–Fritsch–Bobbitt synthesis of isoquinoline alkaloids. Their addition to imine 2 proceeded with partial cyclization, giving isoquinolones (+)-7 and (−)-7 along with acyclic products, (−)-8 and (+)-8, respectively. LAH-reduction of (+)-7 and (−)-7, followed by cyclization, afforded both enantiomers of the alkaloid, (S)-(−)- and (R)-(+)-O-methylbharatamine 5, in 32% and 40% overall yield and with 88% and 73% ees, respectively. 相似文献
4.
Synthesis of enantiopure (Z)-(2′R)-1-O-(2′-methoxyhexadec-4′-enyl)-sn-glycerol 1, the principal methoxylated glyceryl ether found in Nature, is described by a highly convergent five-step process taking place in 27% overall yield. The synthesis is based on an ether bond formation between the chiral synthon (R)-2,3-O-isopropylidene-sn-glycerol and (Z)-(R)-1-chlorohexadec-4-en-2-ol employing ground potassium hydroxide and tetra-n-butylammonium bromide as a catalyst under solvent free conditions. 相似文献
5.
《Tetrahedron: Asymmetry》2003,14(13):1871-1877
(±)-3-Butyryloxyquinuclidinium butyrate 6 (2 M, 571 g/L), prepared from (±)-quinuclidin-3-ol 1 and butyric anhydride, undergoes enantioselective hydrolysis by an Aspergillus melleus protease {1.0% (w/v)} in water in the presence of Ca(OH)2 to keep the reaction at pH 7 and trap butyric acid that is introduced as part of (±)-6 and generated by the enzymatic hydrolysis. After a 24 h period, extraction with n-heptane provides (R)-quinuclidin-3-yl butyrate 5a, which, on methanolysis with Na2CO3, is converted into (R)-1, a common pharmacophore of neuromodulators acting on muscarinic receptors, in 96% ee and 42% overall yield from (±)-1. The unwanted antipode (S)-1, which is extracted into n-butanol and purified via its hydrochloride salt in 89% ee and 40% overall yield from (±)-1, can be racemized by the catalysis of Raney Co at 140°C under an atmosphere of H2 (5 kg/cm2) to regenerate (±)-1 in 97% yield. 相似文献
6.
《Tetrahedron: Asymmetry》2000,11(11):2249-2253
(1S,5R,7R)-(−)-10,10-Dimethyl-3-ethyl-4-oxa-2-azatricyclo[5.2.1.01,5]dec-2-ene 2 was prepared in 95% yield from (1S)-1-amino-2-exo-hydroxyapocamphane 1. The chiral oxazoline could be alkylated (LDA/THF/−78°C/RX, RX=ethyl, n-propyl, n-butyl iodides or benzyl bromide) to 3 in 95% yield and >95% diastereoselectivity, and the products hydrolysed to (R)-2-methylalkanoic acids 4 (43–47% yield, 93–98% e.e.). 相似文献
7.
《Tetrahedron: Asymmetry》2003,14(15):2247-2251
(S)-1-Phenyl-2-(p-tolyl)ethylamine (S)-1, used for the industrial scale resolution of chrysanthemic acids, was obtained via resolution of the racemate with the hemiphthalate of (S)-isopropylidene glycerol (R)-2. The maximum experimental efficiency [69% yield and >99% e.e. of (S)-1] was achieved by a simple precipitation of (S)-1·(R)-2 from the solution of the 1:1 diastereomeric salt mixture in 93/7 isopropanol/water at saturation of the more soluble (R)-1·(R)-2 salt. Such an experimental efficiency was consistent with 0.79 maximum theoretical resolvability, derived from the solubilities of the two diastereomeric salts, and with DSC data, which indicated that the (S)-1·(R)-2/(R)-1·(R)-2 system is a binary mixture exhibiting an eutectic with composition approximately corresponding to a 0.2 molar ratio of (S)-1·(R)-2. 相似文献
8.
This paper describes the selective syntheses of two cis-isomer-enriched cyclopentanone fragrances: (Z)-3-(2-oxopropyl)-2-(pent-2-en-1-yl)cyclopentanone (four steps, 62% overall yield, 67% cis) and Magnolione® (five steps, 60% overall yield, 55% cis). In addition, the asymmetric synthesis of (3aR,7aS)-5-methyl-2,3,3a,4,7,7a-hexahydro-1H-inden-1-one as well as (3a′R,7a′S)-5′-methyl-2′,3′,3a′,4′,7′,7a′-hexahydrospiro[[1,3]dioxolane-2,1′-indene] has been realized by an efficient kinetic resolution, which enables the selective synthesis of the 2S,3R-isomer-enriched 3 and 4. 相似文献
9.
Robert W. Baker Simon O. Rea Elisabeth M.C. Schenkelaars Angela Totaro 《Tetrahedron》2005,61(15):3733-3743
Racemic 1-(1′-isoquinolinyl)-2-naphthalenemethanol rac-12 was prepared through a ligand coupling reaction of racemic 1-(tert-butylsulfinyl)isoquinoline rac-7 with the 1-naphthyl Grignard reagent 10. Resolution of rac-12 was achieved through chromatographic separation of the Noe-lactol derivatives 14 and 15, providing (R)-(−)-12 of >99% ee and (S)-(+)-12 of 90% ee. The ligand coupling reaction of optically enriched sulfoxide (S)-(−)-7 (62% ee) with Grignard reagent 10 furnished rac-12, with the absence of stereoinduction resulting from competing rapid racemisation of the sulfoxide 7. Reaction of optically enriched (S)-(−)-7 with 2-methoxy-1-naphthylmagnesium bromide was also accompanied by racemisation of the sulfoxide 7, and furnished optically active (+)-1-(2′-methoxy-1′-naphthyl)isoquinoline (+)-3b in low enantiomeric purity (14% ee). The absolute configuration of (+)-3b was assigned as R using circular dichroism spectroscopy, correcting an earlier assignment based on the Bijvoet method, but in the absence of heavy atoms. Optically active 2-pyridyl sulfoxides were found not to undergo racemisation analogous to the 1-isoquinolinyl sulfoxide 7, with the ligand coupling reactions of (R)-(+)- and (S)-(−)-2-[(4′-methylphenyl)sulfinyl]-3-methylpyridines, (R)-(+)-17 and (S)-(−)-17, with 2-methoxy-1-naphthylmagnesium bromide providing (−)- and (+)-2-(2′-methoxy-1′-naphthyl)-3-methylpyridines, (−)-18 and (+)-18, in 53 and 60% ee, respectively. The free energy barriers to internal rotation in 3b and 18 have been determined, and the isoquinoline (R)-(−)-12 examined as a ligand in the enantioselectively catalysed addition of diethylzinc to benzaldehyde; (R)-(−)-12 was also converted to (R)-(−)-N,N-dimethyl-1-(1′-isoquinolinyl)-2-naphthalenemethanamine (R)-(−)-19, and this examined as a ligand in the enantioselective Pd-catalysed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate. 相似文献
10.
《Tetrahedron: Asymmetry》2001,12(2):279-285
The enzymatic resolution of 2-fluoroarylacetonitriles (RS)-3 using nitrilase from the plant Arabidopsis thaliana is described. Racemic 2-fluoronitriles 3 are easily accessible from O-silylated aromatic cyanohydrins 2 by reaction with DAST. The nitriles (RS)-3 were hydrolysed with the nitrilase as a catalyst, not to the expected 2-fluoroarylacetic acids but to the corresponding (R)-2-fluoroarylacetamides (R)-5 as the main products. After optimization of reaction conditions (pH 9, 7°C), the enantiomeric excesses of (R)-5a,c and f (R=H, 3-Me, 3-OMe) could be improved to >99% by one recrystallization. The acid catalysed hydrolysis of (R)-5a,5c and 5f afforded the corresponding (R)-2-fluoroarylacetic acids (R)-4a,4c and 4f without racemization. 相似文献
11.
《Tetrahedron: Asymmetry》2001,12(7):1047-1054
A concise asymmetric synthesis of (R)-(+)-methyl 3-amino-3-(5-hydroxy-2-pyridinyl)propanoate 2, a β-amino acid analog of l-azatyrosine 1 starting from the commercially available (−)-Andersen reagent (−)-3 in good overall yield is described. 相似文献
12.
《Tetrahedron: Asymmetry》2001,12(2):293-300
(R,S)-1,3-Butanediol 5 was kinetically resolved by enzymatic acetylation with vinyl acetate under the presence of Chirazyme™ L-2, c–f, yielding (S)-1-O-acetyl-1,3-hydroxybutane 6 and (R)-1,3-di-O-acetyl-1,3-butanediol 7 with enantiomeric excesses of 91% (E=67.3). Compounds 6 and 7 were easily transformed into the corresponding (S)-3-O-(2-methoxyethoxymethyl)-3-hydroxybutanal 10 and (R)-3-benzyloxybutanal 19, through a protection–deprotection and functional group interchange methodology. Subsequent reaction of 10 and 19 with 3-(methoxycarbonylpropionylmethylene)triphenylphosphorane afforded methyl (E,S)-8-O-(2-methoxyethoxymethyl)-4-oxo-5-nonenoate 12 and (E,R)-8-benzyloxy-4-oxo-5-nonenoate 20. The alkenes 19 and 20 were then catalytically hydrogenated to the corresponding saturated esters 13 and 21. Treatment of 13 and 21 with 1,2-ethanedithiol/F3B·OEt2 afforded dithioketals 14 and 22, which were respectively reduced to (S)-1,8-dihydroxy-4-nonanone ethylidenedithioketal 15 and (R)-8-O-benzyl-1,8-dihydroxy-4-nonanone ethylidenedithioketal 23. Finally, deprotection of 15 by catalytic hydrogenation under acidic conditions gave the expected (5S,7S)-(−)-7-methyl-1,6-dioxaspiro[4.5]decane 1. The (5R,7R)-(+)-1 enantiomer was analogously prepared from 23. Both compounds were formed by this procedure with an e.e. of 91%. 相似文献
13.
《Tetrahedron: Asymmetry》2006,17(21):2976-2980
The insect pheromone (2S,3R,7R)-3,7-dimethyltridec-2-yl acetate 1-Ac was prepared from diastereomerically enriched (2S1,3R1,7R)-1, which in turn was obtained by the coupling of racemic 3,4-dimethyl-γ-butyrolactone with (7S)-2-methyloctyllithium, followed by a Wolff–Kishner reduction of the resulting ketone. Conversion of (2S1,3R1,7R)-1 to the corresponding alkyl hydrogen phthalate and diastereomer salt formation with (S)-PhCHMeNH2 provided after several crystallizations individual diastereomer, which was later transformed into target 1-Ac after hydrolysis and acylation. 相似文献
14.
《Tetrahedron: Asymmetry》2006,17(15):2210-2215
Efficient preparations of (R)-(−)-apomorphine (R)-1 and (R)-(−)-aporphine (R)-2 based on a recycle process of resolution are described. In this recycle process of resolution, (RS)-(±)-10,11-dimethoxyaporphine 3 as the precursor of 1, and (RS)-(±)-aporphine 2 were successfully resolved into both enantiomers with (+)-dibenzoyltartaric acid (DBTA). The desired (R)-3 and (R)-2 were obtained and then, respectively, transformed to compound (R)-1, the hydrochloride salt of (R)-1, diacetate compound 4 and the hydrochloride salt of (R)-2; while the undesired (S)-3 and (S)-2 were racemized to obtain a racemate, which was suitable for further resolution. A method for the racemization of the undesired (S)-3 and (S)-2 was extensively studied, in order to obtain high-yielding racemization conditions. A plausible mechanism for the racemization of (S)-3 and (S)-2 was also proposed. 相似文献
15.
Yoko Kameda 《Tetrahedron》2006,62(41):9751-9757
(4R,8R)-4,8-Dimethyldecanal, a common aggregation pheromone of Tribolium flour beetles, has been synthesized from (R)-2,3-O-isopropylideneglyceraldehyde in 11 steps and 7% overall yield. The key step in the synthesis is the highly diastereoselective chelation-controlled radical reaction of ethyl (4S,5R)-4-benzyloxy-5,6-(isopropylidenedioxy)-2-methylenehexanoate with ethyl (R)-5-iodo-3-methylpentanoate performed in the presence of 7 equiv of MgBr2·OEt2. 相似文献
16.
Jie Yu Feng Guo Yun-Qiu Yang Hui-Hui Gao Ru-Yan Hou Xiao-Chun Wan 《Tetrahedron: Asymmetry》2017,28(6):758-761
Both enantiomers of (3Z,9Z)-cis-6,7-epoxy-3,9-octadecadiene, one of which is the major component of the sex pheromone of Ectropis oblique Prout, were synthesized in 23% overall yield for the (?)-(6S,7R)-enantiomer and 18% yield for the (+)-(6R,7S)-isomer. This protocol uses a sequential regioselective ring-opening strategy and provides a convenient and reliable access to other structurally related insect sex pheromones. Preliminary biological studies revealed that (?)-(6S,7R)-2a was roughly as active as the natural pheromone, while racemic (±)-2 was less bioactive and (+)-2b was much less bioactive. 相似文献
17.
《Journal of organometallic chemistry》2007,692(1-3):645-653
A new optically active functionalized tertiary amine, (2R,6R)-2,6-bis(2-hydroxyphenyl)-1-(2-pyridylmethyl)piperidine {(R,R)-1}, was synthesized and its complexation behavior as a tripodal ligand was elucidated with titanium(IV) ion. Protonolysis of Ti(OPr-i)4 with (R,R)-1 and H2O in a stepwise manner led to the formation of C3-symmetric tris(μ-oxo)trititanium(IV,IV,IV) complex [Ti3L3(μ-O)3] {L = diphenolato anion of (R,R)-1} with unified chiralities induced at the metal center (A) and by the conformations of the N∧O chelate loops (λ) as well as the six-membered non-planner chair-like (Ti-μ-O)3 ring core as defined by X-ray crystallography. These stereochemical issues are principally regulated by the stereogenic centers on the ligand and a chair conformation of the piperidine skeleton, which settle an enantiotopos-differentiating cis(Ophenolato–Ophenolato) binding mode by unequivocally locating one Ophenolato in an axial position and the other Ophenolato in an equatorial plane. 相似文献
18.
Mallam Venkataiah Palabindela Somaiah Gowrisankar Reddipalli Nitin W. Fadnavis 《Tetrahedron: Asymmetry》2009,20(19):2230-2233
Goniothalesdiol A 1 has been synthesized from (R)-2,3-O-cyclohexylidine glyceraldehyde with high stereoselectivity and 22% overall yield in 11 simple steps. The key features of the synthetic strategy include the stereocontrolled allylation of (R)-2,3-O-cyclohexylidine glyceraldehydes; the cross-metathesis with a Grubbs’s second generation catalyst, and the intramolecular base-catalyzed oxy-Michael addition for the formation of the tetrahydropyran ring. 相似文献
19.
《Tetrahedron: Asymmetry》2007,18(14):1701-1711
Both enantiomers (8aR)-7 and (8aS)-7 of bicyclofarnesol were synthesized from the enzymatic resolution products (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)-5 (98% ee) and 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)-6 (>99% ee), respectively. The formal synthesis of (+)-wiedendiol 1 was achieved via a coupling reaction of an ate complex derived from 1,2,4-trimethoxybenzene with allyl bromide (8aS)-8 derived from (8aS)-7. The total synthesis of (+)-norsesterterpene diene ester 2 was achieved, based on the synthesis of (13E,10S)-α,β-unsaturated aldehyde 12, derived from (8aS)-7, followed by the selective construction of the (3E,5E)-diene moiety including a C(2)-stereogenic centre in (+)-2. The total synthesis of (−)-subersic acid 3 was carried out based on a Stille coupling between allyl trifluoroacetate congener 25c, derived from (8aR)-7, corresponding to the diterpene part, and aryl stannane congener 26 in the presence of Pd catalyst and CuI as an additive. 相似文献
20.
《Tetrahedron: Asymmetry》2005,16(16):2810-2815
Saccharomyces cerevisiae, strain DBM 2115, was successfully employed in the reduction of the separated Z- and E-isomers of ethyl 4-[(2-oxocyclohexyl)methyl]phenoxy-3-methyl-2-butenoates 1 and 2, in order to prepare the (1S,2S)- and (1R,2S)-enantiomers of the corresponding ethyl 4-[(2-hydroxycyclohexyl)methyl]phenoxy-3-methyl-2-butenoates 3–6. The products were obtained with the required absolute configuration: (1S,2S)-3 (ee = 98%; yield 48%), (1R,2S)-4 (ee = >99%; yield 45%), (1S,2S)-5 (ee = 98.5%; yield 47%), and (1R,2S)-6 (ee = >99%; chemical yield 44%). 相似文献