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1.
[reaction: see text] A short and highly efficient route to D- and L-talo-gamma-lactones has been developed. The key transformation was the sequential osmium-catalyzed bis-dihydroxylation reaction of substituted 2,4-dienoates. When the first dihydroxylation reaction is performed on (2Z,4E)-dienoates with use of the Sharpless AD-mix procedure, a regio- and enantioselective dihydroxylation resulted along with an in situ lactonization. A subsequent dihydroxylation, using OsO4/NMO in MeOH conditions, resulted in an exceedingly diastereo- and enantioselective synthesis of talo-gamma-lactone. 相似文献
2.
Christophe Len Abdelmajid Sélouane Asa WeilingFabien Coicou Denis Postel 《Tetrahedron letters》2003,44(4):663-666
Both enantiomers of 3-benzoyloxymethylisobenzofuranone have been obtained in good yield in six steps from phthalaldehyde using a d-xylose derivative as a chiral protecting group. The two chiral heterocycles are γ-hydroxymethyl-α,β-butenolide analogues having a benzene ring in positions 2 and 3. The key step was the dihydroxylation using both OsO4 and AD-mix developed by Sharpless. The asymmetric dihydroxylation using AD-mix required a double diastereoselectivity and gave excellent diastereoisomeric excess. 相似文献
3.
Hari Babu Mereyala P. Mallikarjun Goud Rajendrakumar Reddy Gadikota Rama Krishna Maddala K. Ramasubba Reddy 《Journal of carbohydrate chemistry》2013,32(9):1201-1210
ABSTRACT Asymmetric dihydroxylation of vinyl furanosides 1-6 by use of OsO4, AD-mix-α® and β® is described yielding the corresponding hexofuranose sugars. Vinyl furanosides 2 and 3, with an ester group at C-3, and vinyl manno furanoside 5 on asymmetric dihydroxylation with AD-mix α® exhibited high R diastereoselectivity at C-5. Reversal in diastereoselectivity at C-5 was observed for the 3-deoxy vinyl furanoside 6 giving furanosaccharide 6S with the S configuration at C-5. 相似文献
4.
Sharpless asymmetric dihydroxylation at the terminal olefin of benzoates 3a and 3b, using both AD-mix α and AD-mix β afforded only one diastereomer of diols 5a and 5b, respectively. Diols 5a and 5b were easily transformed into cis- and trans-2,5-disubstituted tetrahydrofurans 7 and 14, respectively, which were subsequently converted into known compounds 12 and 19. 相似文献
5.
Application of the Buchwald protocol to the coupling of o-bromobenzoates and 1-tetralones directly affords benzodihydronaphthopyrones with a fused tetracyclic system. Aromatization of the 7,8-dimethoxy-2,3-methylenedioxy derivative yielded arnottin I, whereas oxidation with dioxirane afforded dihydroarnottin II composed of a spiro phthalide-tetralone system. Sharpless asymmetric dihydroxylation using AD-mix yielded optically active dihydroarnottin II with good enantioselectivity. The absolute stereochemistry of the stereogenic center in the (+)-spiro product was determined to be R by X-ray crystallographic analysis of the dibromo derivative. (+)-Dihydroarnottin II was subjected to successive bromination and dehydrobromination to prepare (-)-arnottin II. The R-configuration of natural (-)-arnottin II, previously assigned by application of the exciton chirality method to the Cotton effects observed in the CD spectrum, was confirmed by asymmetric synthesis. 相似文献
6.
The combination of a Wittig olefination and a dihydroxylation reaction constitutes a facile synthetic protocol for the transformation of unprotected carbohydrates into higher sugars. The Wittig reaction is carried out with tert-butyl or diphenylmethyl ester stabilized phosphoranes to give (E)-configured alpha,beta-unsaturated esters as the only products in most cases. These are dihydroxylated in a diastereoselective fashion using OsO(4)/NMO. The stereochemical outcome in the dihydroxylation follows Kishi's empirical rule and gives high diastereoselectivity (5:1-8:1) when starting from sugars with the 2,3-threo configuration. When starting from sugars with the 2,3-erythro configuration, the diastereoselectivity in the dihydroxylation is low (2:1-2.5:1). As a result, the Wittig/dihydroxylation protocol is most effective for producing higher sugars with the galacto configuration at the reducing end. The two steps can either be carried out individually or, more efficiently, as a one-pot procedure. 相似文献
7.
A series of polyhydroxylated bicyclic nucleoside derivatives is approached applying stereoselective dihydroxylation reactions. Three out of four isomeric and protected products were obtained after the stereoselectivity of dihydroxylation has been completely inverted comparing a bicyclic nucleoside with a tricyclic furanose substrate. A corresponding 2'-deoxynucleoside derivative has been obtained after an optimized deoxygenation procedure. 相似文献
8.
Peroxophosphotungstate held in an ionic liquid brush: an efficient and reusable catalyst for the dihydroxylation of olefins with H2O2 in neat water
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Xian‐Ying Shi Peng‐Min Wang Ke‐Yan Liu Xue‐Fen Dong Xiao‐Yan Han Jun‐Fa Wei 《应用有机金属化学》2014,28(10):760-763
A reusable heterogeneous catalytic assembly of [PO4{WO(O2)2}4]3? held in an ionic liquid brush was synthesized and an environmentally friendly procedure was developed for the dihydroxylation of several olefins with 30 wt% H2O2. These reactions were conducted in neat water under mild conditions without any organic co‐solvent or other additive. Several factors that affect the dihydroxylation were investigated in detail. The catalyst is easily recovered after the reaction via simple filtration, and can be reused at least eight times without a noticeable loss of activity. The experimental results demonstrate that this dihydroxylation process has no apparent scale‐up effect. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
1,4-双(9-O-奎宁)-2,3-二氮杂萘的合成及其在烯烃不对称二羟基化反应中的应用 总被引:5,自引:0,他引:5
通过改进的文献方法制备1,4-双(9-O-奎宁)-2,3-二氮杂萘[(QN)2PHAL].在碱性条件下,奎宁与1,4-二氯-2,3-二氮杂萘之间的亲核取代反应以72%的化学产率生成(QN)2PHAL.在4种烯烃的不对称二羟基化反应中,(QN)2PHAL表现出很高的对映选择性(83%~92%e.e.)和催化活性(产率83%~93%). 相似文献
10.
Iliyas A. Sayyed 《Tetrahedron》2005,61(11):2831-2838
A simple and effective procedure for the enantioselective synthesis of several β-adrenergic blocking agents incorporating the first asymmetric synthesis of celiprolol, is described. The key steps are (i) sharpless asymmetric dihydroxylation of aryl allyl ethers to introduce chirality into the molecules and (ii) conversion of cyclic sulfates into the corresponding epoxides using a three-step procedure. 相似文献
11.
Majid M. Heravi Vahideh Zadsirjan Maryam Esfandyari Tahmineh Baie Lashaki 《Tetrahedron: Asymmetry》2017,28(8):987-1043
Sharpless asymmetric dihydroxylation involves the reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form an optically active vicinal diol. This reaction was primarily developed by Sharpless based on the already known racemic Upjohn dihydroxylation. The chiral diols obtained by Sharpless asymmetric dihydroxylation are important intermediates in organic synthesis. Herein, we emphasise the applications of Sharpless asymmetric dihydroxylation in the total synthesis of natural products. 相似文献
12.
Dr. Peter K. Dornan Zachary K. Wickens Prof. Robert H. Grubbs 《Angewandte Chemie (International ed. in English)》2015,54(24):7134-7138
A stereoselective synthesis of anti‐1,2‐diols has been developed using a multitasking Ru catalyst in an assisted tandem catalysis protocol. A cyclometalated Ru complex catalyzes first a Z‐selective cross‐metathesis of two terminal olefins, followed by a stereospecific dihydroxylation. Both steps are catalyzed by Ru, as the Ru complex is converted to a dihydroxylation catalyst upon addition of NaIO4. A variety of olefins were transformed into valuable, highly functionalized, and stereodefined molecules. Mechanistic experiments were performed to probe the nature of the oxidation step and catalyst inhibition pathways. These experiments point the way to more broadly applicable tandem catalytic transformations. 相似文献
13.
近年来,人们对催化不对称二羟基化反应进行了广泛和深入的研究.前文曾报道了邻位取代的(E)-1,2-二苯乙烯的不对称二羟基化反应.本文探讨了对位取代的(E)-1,2-二苯乙烯类化合物的合成. 相似文献
14.
The bacterial strain Sphingomonas sp. HXN-200 was used to catalyze the trans dihydroxylation ofN-substituted 1,2,5,6-tetrahydropyridines 1 and 3-pyrrolines 4 giving the corresponding 3,4-dihydroxypiperidines 3 and 3,4-dihydroxypyrrolidines 6, respectively, with high enantioselectivity and high activity. The trans dihydroxylation was sequentially catalyzed by a monooxygenase and an epoxide hydrolase in the strain with epoxide as intermediate. While both epoxidation and hydrolysis steps contributed to the overall enantioselectivity in trans dihydroxylation of 1, the enantioselectivity in trans dihydroxylation of the symmetric substrate 4 was generated only in the hydrolysis of meso-epoxide 5. The absolute configuration for the bioproducts (+)-3 and (+)-6 was established as (3R,4R) by chemical correlations. Preparative trans dihydroxylation of 1a and 4b with frozen/thawed cells of Sphingomonas sp. HXN-200 afforded the corresponding (+)-(3R,4R)-3,4-dihydroxypiperidine 3a and (+)-(3R,4R)-3,4-dihydroxy pyrrolidine 6b in 96% ee both and in 60% and 80% yield, respectively. These results represent first examples of enantioselective trans dihydroxylation with nonterpene substrates and with bacterial catalyst, thus significantly extending this methodology in practical synthesis of valuable and useful trans diols. Enantioselective hydrolysis of racemic epoxide 2a with Sphingomonas sp. HXN-200 gave 34% of (-)-2a in >99% ee, which is a versatile chiral building block. Further hydrolysis of (-)-2a with the same strain afforded (-)-(3S,4S)-3a in 96% ee and 92% yield. Thus, both enantiomers of 3a can be prepared by biotransformation with Sphingomonas sp. HXN-200. 相似文献
15.
16.
Robert R. France Ian Cumpstey Terry D. Butters Antony J. Fairbanks Mark R. Wormald 《Tetrahedron: Asymmetry》2000,11(24):343-4994
2-Aminobenzamide (2AB) is a common fluorescence label attached to reducing oligosaccharides by a reductive amination procedure. Chemical investigation of the published literature procedure reveals labelling occurs by the expected mechanism for both protected and unprotected glucose derivatives to yield open-chain carbohydrates rather than result in the formation of any heterocyclic materials. Pentenyl glucosides may also be readily attached to the 2AB label by a sequence of dihydroxylation, periodate cleavage and subsequent reductive amination of the resulting aldehyde. 2AB labelling is compatible with deprotection of both acetate and benzyl protecting groups. 相似文献
17.
XuanJiaPENG XueGongSHE ZiKunWANG WeiGuoQUAN XinFuPAN 《中国化学快报》2005,16(2):186-188
An asymmetric total synthesis of mansonone P and R were achieved, in which introduction of hydroxy substituent at position 2 was performed by Sharpless dihydroxylation of sily enol ether. 相似文献
18.
Md. Moinuddin Ahmed 《Tetrahedron letters》2005,46(17):3015-3019
A highly efficient route to various 1,5-galacto-sugar lactones from dienoates has been developed by using three catalytic reactions. These reactions include (i) an enantioselective osmium-catalyzed dihydroxylation, (ii) a regio- and diastereoselective palladium-catalyzed π-allyl alkylation with p-methoxyphenol for alcohol differentiation and protection, and (iii) a diastereoselective dihydroxylation that can be improved using matched enantioselective osmium-catalyzed dihydroxylation condition. 相似文献
19.
A biomimetic catalytic system for dihydroxylation of olefins consisting of OsO4, N-methylmorpholine, and a flavin has been immobilized in an ionic liquid. This immobilized catalytic system is highly efficient for dihydroxylation with 30% aqueous H2O2 and it can be reused (at least 5 times) without loss of activity. 相似文献
20.
A simple and convenient route is presented for the preparation of regio- and stereoisomers of novel azepane β-amino esters, starting from bicyclic β-lactam isomers. The synthetic procedure consists of dihydroxylation of the olefinic bond of the alicyclic amino esters, followed by NaIO4-mediated cleavage of the diol intermediate and reductive ring closure, which furnishes novel regioisomeric 5-aminoazepane-4-carboxylate and 3-aminoazepane-4-carboxylates. This method also allows the preparation of amino esters with an azepane skeleton in enantiomerically pure form. 相似文献