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1.
Full details for the total synthesis of (±)-nominine, a hetisine-type aconite alkaloid, are presented in three parts. Here (part 1), we describe the preparation of the key tetracyclic intermediate 6. Our palladium-catalyzed intramolecular α-arylation was adopted for preparation of the intermediate 4 with an angular formyl group. An acetal-ene reaction was then employed for C14-C20 bond formation to secure 6 from 5. The reaction mechanism of the acetal-ene reaction is discussed, and a method for removal of the 2-hydroxyethyl group from 6 is developed.  相似文献   

2.
Delphine Didier 《Tetrahedron》2007,63(18):3864-3869
In this paper, we report the synthesis of amino and aminomethyl derivatives of Tröger's base (±)-1 and (±)-2. The key steps in the synthesis of (±)-1 and (±)-2 are Pd-catalyzed amination and cyanation, respectively, of the easily accessible dihalo derivatives (±)-3. These compounds are important intermediates in the synthesis of new ligands and building blocks for H-bonded supramolecular architectures.  相似文献   

3.
The novel optically active derivatives of 2,2′-disubstituted-1-aminocyclopropane-1-carboxylic acid (−)-2 and (+)-3 were synthesised from the spiro-azlactone (+)-1. Oxidation of the diol moiety of (+)-3 gave by ring enlargement the racemic mixture of 2,3-dihydrofuran derivative (±)-6. This conversion is explained by stepwise rearrangement of the initially formed tetrasubstituted cyclopropanecarbaldehyde 4 through zwitterionic's reactive intermediate 5. The formation of (±)-6 is preferred energetically as established by ab initio calculations of the ground states and possible intermediates for that rearrangement. The crystal structure and absolute configuration of the compounds (+)-1, (−)-2, (+)-3 and (−)-7 were determined by single-crystal X-ray diffraction method. All four compounds possess Z-configuration of the cyclopropane ring. The dioxolane ring in the structures (+)-1 and (−)-2 adopts half-chair conformation, while the cyclopropane ring and geminally substituted groups in the structures (−)-2, (+)-3 and (−)-7 possess the anticlinal conformation. The molecules of the compound (+)-1 are connected by very weak intermolecular hydrogen bond of C-H?O type. In the compounds (−)-2, (+)-3 and (−)-7inter- and intramolecular hydrogen bonds of N-H?O type were observed. The spiro-compound (+)-1 exhibited a more pronounced inhibitory activity against the proliferation of murine leukemia and human T-lymphocytes cells than other type of tumor cell lines and normal human fibroblast cells.  相似文献   

4.
The asymmetric synthesis of new tetrahydropyrrolo[2,3-b]indole 19 and tetrahydropyrano[2,3-b]indole 20 rings, substituted in position C-3a and C-4a with a hydroxy- and an amino functionalized chain, respectively, was performed starting from the racemic spiro[cyclohexane-1,3′-indoline]-2′,4-diones 7. The enantiopure spiro oxo-azepinoindolinone (+)-10, obtained from (±)-7 by the way of an asymmetric ring enlargement, and the amino acid (+)-14, obtained by the hydrolysis of 10, were prepared as key intermediates for the synthesis of enantiopure compounds (−)-19 and (−)-20. Since the amino acid 14 is the common intermediate for the chemoselective preparation of derivatives 19 and 20, experimental and computational studies were performed in order to selectively obtain these compounds and to provide a mechanistic rationalization for their formation.  相似文献   

5.
(±)-Untenone A, one of the marine cyclopentanoids, has been conveniently synthesized via (±)-cis-1-hexadecylcyclopent-2-en-1,4-diol 9 which has been produced from 1-hexadecylcyclopenta-1,3-diene 6 via photo-oxidation and the following reduction. The key step of the present synthesis is the selective alkylation of cyclopenta-1,3-diene to form 6. Optically active (−)- and (+)-untenone A have been prepared from (−)- and (+)-9, respectively, after enzymatic kinetic resolution of (±)-9.  相似文献   

6.
Olena Affolter 《Tetrahedron》2009,65(33):6626-4417
Baeyer-Villiger oxidations of several tropane derivatives have been investigated. Whereas tropenones 15a-c underwent exclusive epoxidation to 21a-c, the corresponding 6-oxotropane derivative 28 yielded the desired lactone 29. Baeyer-Villiger oxidation was also possible for the O-isopropylidene-protected diols 32a,b. The resulting lactones 33a,b were employed in the total synthesis of (±)-7a-epi-hyacinthacine A1 (7a-epi-7) via an intramolecular nucleophilic alkyllithium addition to a carbamate as the key lactamization step. The target compound was prepared from tropenone 15b in 10 steps and 14% overall yield. Enzymatic resolution of pyrrolidine (±)-36 provided a formal total synthesis to both enantiomers of 7.  相似文献   

7.
Full details of the biomimetic conversion of polyene metabolite spectinabilin (5) into the isomeric natural products SNF4435C (1) and SNF4435D (2) by a cascade of E/Z-isomerizations and electrocyclizations are reported. Additionally, short total syntheses of the related natural products (±)-aureothin (3), (±)-N-acetyl-aureothamine (4) and (±)-spectinabilin (5) are presented. The key steps in the synthesis of (±)-3, (±)-4 and (±)-5 are the construction of the tetrahydrofuran motif using a palladium-catalyzed cycloaddition and the ruthenium-catalyzed cross metathesis of alkene 17 to form the common intermediate, boronic ester 24, which was further transformed using a trans-selective Suzuki coupling with a dibromide and a stereospecific Negishi-type methylation.  相似文献   

8.
A synthesis of functionalized phenolic α-amino-alcohol (±)-13 as synthetic precursor of the catechol tetrahydroisoquinoline structure of phthalascidin 650 is disclosed. Starting from 3-methylcatechol 5, eight steps of synthesis give rise to the synthesis of phenolic α-amino-alcohol (±)-13 in 27% overall yield. This synthetic strategy involves the elaboration of fully functionalized aromatic aldehyde 8 and its transformation into a phenolic α-amino-alcohol (±)-13, through a Knoevenagel condensation, simultaneous reduction of nitroketene and ester functions and hydrogenolysis of the benzyl protecting group. The pentacycle (±)-18 was obtained after four additional steps. The Pictet-Spengler cyclisation between the phenolic α-amino-alcohol (±)-13 and N-protected α-amino-aldehyde 4 allowed to obtain (1,3′)-bis-tetrahydroisoquinoline 14 with N-methylated and N-Fmoc removed. The last step was a Swern oxidation for allowing an intramolecular condensation.  相似文献   

9.
Stereocontrolled total syntheses of the bridged tricyclic ketones (±)-clovan-3-one (5) and (±)-epi-clovan-3-one (6) and a facile total synthesis of the tricyclic sesquiterpene (±)-pseudoclovene-A (3) have been successfully accomplished involving participation of an aryl intramolecular cyclisation of the bromophenol 11 as a key step.  相似文献   

10.
The first total synthesis of tetrahydrobenzo[a]anthraquinone natural product (±)-zenkequinone B (1) is reported. The key step involves the TiCl4-promoted intramolecular cyclization of 4-aryl-2-hydroxybutanal diethyl acetal 4 to give compound 3. The total synthesis of (±)-zenekequinone B (1) has been accomplished in five steps from readily available 2-(chloromethyl)-9,10-dimethoxyanthracene (5) in 40.3% overall yield.  相似文献   

11.
A series of (±)3-hydroxyl- and 2,3-dihydroxy-2,3-dihydro-7-oxopyrido[3,2,1-de]acridines were synthesized for antitumor evaluation. These agents can be considered as analogues of glyfoline or (±)1,2-dihydroxyacronycine derivatives. The key intermediates, 3,7-dioxopyrido[3,2,1-de]acridines (15a,b or 24a,b), for constructing the target compounds were synthesized either from 3-(N,N-diphenylamino)propionic acid (14a,b) by treating with Eaton’s reagent (P2O5/MsOH) (Method 1) or from (9-oxo-9H-acridin-10-yl)propionic acid (23a-c) via ring cyclization under the same reaction conditions (Method 2). Compounds 15a,b and 24a,b were converted into (±)3-hydroxy derivatives (25a-d), which were then further transformed into pyrido[3,2,1-de]acridin-7-one (28a-d) by treating with methanesulfonic anhydride in pyridine via dehydration. 1,2-Dihydroxylation of 28a-d afforded (±)cis-2,3-dihydroxy-7-oxopyrido[3,2,1-de]acridine (29a-d). Derivatives of (±)3-hydroxy (25a,b) and (±)cis-2,3-dihydroxy (29a-d) were further converted into their O-acetyl congeners 26a,b and 30a-d, respectively. We also synthesized 2,3-cyclic carbonate (31, 32, and 33) from 29a-c. The anti-proliferative study revealed that these agents exhibited low cytotoxicity in inhibiting human lymphoblastic leukemia CCRF-CEM cell growth in culture.  相似文献   

12.
Lipase-catalyzed acylation of 2-hydroxyiminomethyl-1,1′-binaphthyl [(±)-1] and hydrolysis of 2-acetoxyiminomethyl-1,1′-binaphthyl [(±)-2] yielded optically active oximes 1 and 2 with high enantiomeric excess. Successful synthesis of the optically active aldehyde 4 from chiral O-acetyl oxime 2 occurred without a decrease of enantiomeric excess.  相似文献   

13.
Robert ?ysek 《Tetrahedron》2007,63(28):6558-6572
Starting from (±)-7-oxanorbornenone ((±)-14), (±)-(1RS,2RS,3SR,6SR)-6-azidocyclohex-4-en-1,2,3-triol ((±)-24) and (±)-(1RS,2RS,3SR,6RS)-6-azidocyclohex-4-en-1,2,3-triol ((±)-26) were obtained. Epoxidation of the latter cyclohexene derivative gave two epoxides (±)-30 and (±)-31 that were converted into (±)-conduramine F-1 epoxides (±)-10 and (±)-11 and N-substituted derivatives (±)-12 and (±)-13. Compound (±)-(1RS,2SR,3RS,4SR,5RS,6SR)-5-({[4-(trifluoromethyl)phenyl]methyl}amino)-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-12c) is a good, non-competitive inhibitor of β-xylosidase from Aspergillus niger (Ki=2.2 μM), and (±)-(1RS,2RS,3SR,4RS,5SR,6SR)-5-{[(biphenyl-4-yl)methyl]amino}-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-13d) is a good inhibitor of α-glucosidase from brewer's yeast (Ki=2.8 μM, non-competitive).  相似文献   

14.
The enantioselective synthesis of the ketones 3 which displays the carbon core of NGF-inducing cyathane diterpenes is described. The key tricyclic trienone 22 was assembled in 13 steps from Michael adduct (R)-8a via intramolecular Heck cyclization of the chiral triflate 21. The trienone 22 was further elaborated into ketone 3 through trimethylaluminum-promoted expansion of the C-ring with trimethylsilyldiazomethane.  相似文献   

15.
The absolute stereochemistry of plakortone E, a cytotoxic metabolite of the Caribbean sponge, was established to be 1, by the synthesis of the racemic C-8 epimer (±)-2 and then of (−)-1 itself, which was identical with the natural compound.  相似文献   

16.
A novel and efficient synthesis of (−)-8-epi-swainsonine 2 is reported. Stereocontrolled diol formation from the bicyclic alkene 3 followed by a stereoselective vinylation of the aldehyde and ring closing metathesis gave the indolizidine ring system, which was converted into (−)-8-epi-swainsonine 2.  相似文献   

17.
Heats of formation have been derived from G3(MP2)//B3LYP and G3MP2B3(+) atomization energies for tert-butyl radical (6R), cubyl radical, bicyclooctyl radical (1R), and tricyclo[3.3.n.03,7]alk-3(7)-yl (n=0-3, 2R-5R) radicals, and their respective anions (1A-6A) and hydrocarbons (1H-6H). The electron affinity (EA) of 6R is estimated at 1.5±2 kcal/mol and tert-butyl anion (6A) is likely to be bound. In the homologous series 2R-5R the EAs range from 3.4±2 to 13.5±2 kcal/mol. The computed enthalpies of the acidities of the tricyclic hydrocarbons 1H-5H are in the range 407-411 kcal/mol. Their C-H bond dissociation energies (BDEs) are in the range 97-110 kcal/mol. The increase of the BDEs in the homologous series 2H-5H and the increase of EAs of 2A-5A is attributed to the enhanced pyramidalization induced in radicals 2R-5R by the shortening of the methylene chain connecting carbons C3 and C7.  相似文献   

18.
Candida antarctica lipase-catalyzed hydrolysis of O-butyryl-BINOL [(±)-3] or O-butyryl-6,6′-dibromo-BINOL [(±)-5] yielded optically active BINOL [(R)-1] or 6,6′-dibromo-BINOL [(R)-4] with high enantiomeric excess at 80 °C. Reaction temperature and acyl group of substrate had a great influence on the reactivity and enantioselectivity, respectively, of lipase-catalyzed hydrolysis for chiral binaphthol synthesis.  相似文献   

19.
This paper presents the chemistry of ethylenediamines and fluorosilanes. The synthesis of thermally stable monosilyl (1-5)- and bis(fluorosilyl)ethylenediamines (6) is described. Starting with the dilithium salt of ethylenediamine and F2Si(CMe3)2 the five-membered 1,3-diaza-2-silacyclopentane (8) is obtained. The reaction of tetra- and trifluorosilanes with dilithiated bis(silyl)ethylenediamines leads to the formation of 1,3-diaza-2-fluorosilylsilacyclopentanes (9-14). Fluorosilanes substitute 8 in 1 and 3 positions (15-28). A fluorosilyl-bridged five-membered ring (29) is isolated in the reaction of 1-trimethylsilyl-1,3-diaza-2-silacyclopentane, BuLi and MeSiF3. In the synthesis of N-fluorosilyl-1,3-diaza-2-silacyclopentanes constitutional isomers were formed (30-33). Quantum-chemical calculations support the isomerisation mechanism. An iminosilane with an SiN double bond is the intermediate product of the rearrangement process.Crystal structures of 7, 13, 20 and 23 are reported.  相似文献   

20.
The enantioselective synthesis of indolizidines (−)-203A, (−)-209B, (−)-231C, (−)-233D, and (−)-235B″ has been achieved and the absolute stereochemistry of both indolizidines 203A and 233D was established as 5S,8R,9S. The relative stereochemistry of natural 231C was established by the present asymmetric synthesis.  相似文献   

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