共查询到20条相似文献,搜索用时 15 毫秒
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《Tetrahedron: Asymmetry》2007,18(18):2218-2226
The trans-configured fosfomycin analogue, diethyl (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonate, was synthesised by the intramolecular Williamson reaction of diethyl (1S,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate. The cis-analogue was obtained as O-ethyl or O,O-diethyl (1R,2S)-1,2-epoxy-3-hydroxypropylphosphonates, when (1R,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate or its 3-O-trityl derivative were used as starting materials, respectively. The intramolecular Williamson cyclisations of diethyl (1S,2R)- and (1R,2S)-1-benzyloxy-3-hydroxy-2-mesyloxypropylphosphonates led to diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, respectively, with the concomitant formation of diethyl (E)-1-benzyloxy-3-hydroxyprop-1-en-1-phosphonate. From diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, enantiomerically pure diethyl (1S,2S)- and (1R,2S)-1,2-dihydroxypropylphosphonates were obtained by catalytic hydrogenation, while diethyl (1S,2S)- and (1R,2S)-3-acetamido-1,2-dihydroxypropylphosphonates were produced after epoxide ring opening with dibenzylamine, acetylation and hydrogenolysis. 相似文献
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R.B. Nasir BaigN.Y. Phani Kumar Jamsad MannuthodikayilSrinivasan Chandrasekaran 《Tetrahedron》2011,67(17):3111-3118
Herein we present a simple and highly efficient method for the synthesis of β and γ-amino thiols via regioselective ring opening of sulfamidates with tetrathiomolybdate 1. The generality of this methodology has been shown by synthesizing carbohydrate derived β-amino thiol. The scope and versatility of this methodology has been demonstrated by synthesizing biologically important unnatural amino acids like isocysteines in optically pure form. 相似文献
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Treatment of 1-benzyl-2-(bromomethyl)aziridine, and some aryl substituted analogues, with an excess of iodomethane resulted in N-allyl-N-benzyl-N,N-dimethylammonium salts, in good yields. These quaternary allylammonium salts are of importance in different fields, from organic synthesis and polymeric chemistry to agricultural use. 相似文献
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A 6-alkyl-4,5-epoxy-6-hydroxy-2-cyclohexen-1-one derivative, a model compound for the hydrophilic moiety of scyphostatin, was stereoselectively synthesized from the Diels-Alder adduct. The key steps were the reductive cleavage of the 4,5-epoxide ring of the epoxidated adduct, the 1,3-carbonyl transposition of the 3-carbonyl group to the C1 position by a Wharton reaction and stereoselective bromination to provide a trans bromohydrin derivative, a precursor to the desired compound. Desilylation of the bromohydrin derivative with TBAF directly gave the target compound. 相似文献
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The novel functionalized N,N′-[2-(arylsulfonamido)propane-1,3-diyl]bis(N-allylarylsulfonamide) and N,N′-[2-(methylsulfonamido)propane-1,3-diyl]bis(N-benzylarylsulfonamide) derivatives have been prepared from 2-(bromomethyl)-1-sulfonylaziridines for the first time using substituted arylsulfonamides in the presence of sodium methoxide under catalyst-free condition in good yields. 相似文献
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The stereoselective syntheses of 2,3-dideoxy-4-oxo-5a-carba-alpha- d-rhamnopyanose 1-phosphate, 2,3-dideoxy-5a-carba-alpha- d-rhamnopyranose 1-phosphate, 5a-carba-alpha- d-rhamnopyranose 1-phosphate, 5a-carba-beta- d-digitoxopyranose 1-phosphate, and 5a-carba-alpha- l-rhamnopyranose 1-phosphate have been achieved from d-quinic acid. The routes rely upon a Simmons-Smith cyclopropanation and diastereospecific ring opening of cyclopropanol under Pd/C hydrogenation condition to set up the alpha-methyl ketone. A sequence of diastereoselective reduction, dihydroxylation, and/or Myers' reductive 1,3-rearrangement were used to install the desired stereochemistry. 相似文献
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The reactivity of 2-(t-butoxycarbonylmethyl)aziridine-1-carboxylic acid benzyl ester has been studied with various N-nucleophiles. The ring-opening reaction was always regioselective, the nucleophile attacking preferentially the less hindered carbon of the aziridine. The reaction was used to prepare a methyleneamino pseudodipeptide using the α-amine of a lysine ester. 相似文献
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Li-juan Meng B.V.D. Vijaykumar Hua Zuo Zhu-Bo Li Gautam Dupati Kiwan Jang Dong-Soo Shin 《Tetrahedron: Asymmetry》2012,23(14):1029-1037
With the aim of discovering new molecules with potassium channel activating properties, we have designed and synthesized derivatives with structural similarity to cromakalim, an important molecule which shows specific affinity toward potassium channels, based on previous structure–activity investigations by applying different C-4 substitutions. This has been accomplished by using a stereoselective Jacobsen epoxidation and microwave assisted regioselective epoxide opening with neutral alumina as the key reactions. 相似文献
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Philippe Remuzon Daniel Bouzard Claire Clemencin Christian Dussy Munir Essiz Jean-Pierre Jacquet Jean Saint-Germain 《Journal of heterocyclic chemistry》1993,30(2):517-523
The synthesis of (1S,4S,7S)- and (1R,4R,7S)-2-(4-tolylsulfonyl>5-phenylmethyl-7-rnethyl-2,5-diazabicyclo-[2.2.1]heptanes ( 20 ) and ( 22 ) from trans 4-hydroxy-L-proline is described. 相似文献
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[reaction: see text] 3-Iodo allenoates were generated in situ and utilized, for the first time, in the ring opening of oxiranes in a regioselective fashion. This simple one-pot three-component reaction protocol provides easy access to highly functionalized homoallylic alcohols in good yields and moderate to very good (Z/E) selectivity. The two functional groups (ester and halogen) can be further subjected to many synthetic transformations. 相似文献
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Recent developments in regioselective ring opening of aziridines 总被引:1,自引:0,他引:1
Pengfei Lu Author Vitae 《Tetrahedron》2010,66(14):2549-542
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Highly regioselective ring opening of epoxides and aziridines using (bromodimethyl)sulfonium bromide
Epoxides and aziridines undergo ring opening efficiently with (bromodimethyl)sulfonium bromide at room temperature to form the corresponding β-bromohydrins and β-bromoamines, respectively. The conversions are highly regioselective and afford the products in excellent yields within a short period of time. 相似文献
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The fluorinated amino acid, (2S,3S)-3'-fluoroisoleucine 3, has been synthesised by a route involving stereoselective cuprate or photochemical addition to the compound 4, derived in turn from (2S)-pyroglutamic acid. This provides a reporter group for the hydrophobic amino acid (2S)-isoleucine for use in protein studies. 相似文献
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Thanks to the successive use of two esterases with different regioselectivities and conventional organic chemistry we have synthesized (1R,2S) and (1S,2S) dehydrocoronamic acids. 相似文献
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Gabriela Mancilla 《Tetrahedron》2008,64(51):11732-11737
Sn(OTf)2 is an efficient and versatile catalyst for the highly regioselective opening of styrene oxide with aromatic amines, which allowed for the preparation of fourteen 2-arylamino-2-phenylethanols, some of them described here for the first time (6g, 6i, 6j, 6k and 6m). Sn(OTf)2 also catalyses the opening of styrene oxide with aliphatic amines in moderate to high yields but with a lower degree of regioselectivity. 2-Akylamino-1-phenylethanols are the predominant products when moderate to high regioselectivity is observed (compounds 4b, 4c and 4d). This is the first report of the use of Sn(OTf)2 to catalyse the opening of an epoxide by aliphatic amines. 相似文献
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Rosario Torregrosa 《Tetrahedron》2007,63(2):469-473
The reaction of different epoxides with commercially available imidazole at 60 °C leads to the formation of the corresponding 1-(β-hydroxyalkyl)imidazoles in a regioselective manner. When the reaction is applied to a chiral epoxide [(R)-styrene oxide], the expected chiral alcohol is isolated with the same enantiomeric excess. The use of benzimidazole as the heterocyclic component in the same process also allows the simple preparation of the corresponding 1-(β-hydroxyalkyl)benzimidazoles. 相似文献
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3-Acylchromones and 3-acylflavones, readily available by acylation of 2′-hydroxydibenzoylmethane with acid anhydrides in the presence of base, undergo efficient conjugate reduction with NaBH4 in pyridine to give the corresponding chroman-4-ones/flavanones in high yields. The reduction is both regio- and chemoselective. Treatment of the chroman-4-ones with MeSO3H generates the 3-alkenyl-2-arylchromones by a dehydrative rearrangement initiated by retro-Michael cleavage of the pyranone ring. This reduction-rearrangement sequence can be extended to 2-alkyl-3-alkenoylchromones to generate 3-alkenyl-2-styrylchromones, the first examples of 2,3-dialkenylchromones. 相似文献