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1.
Meruva Suresh Babu Akula Raghunadh Konda Ramulu Vilas H. Dahanukar Unniaran K. Syam Kumar P. Kumar Dubey 《Helvetica chimica acta》2014,97(11):1507-1515
A highly enantiospecific, azide‐free synthesis of (?)‐(R)‐ and (+)‐(S)‐piperidin‐3‐ol in excellent yield was developed. The key step of the synthesis involves the enantiospecific ring openings of enantiomerically pure (R)‐ and (S)‐2‐(oxiran‐2‐ylmethyl)‐1H‐isoindole‐1,3(2H)‐diones with the diethyl malonate anion and subsequent decarboxylation. 相似文献
2.
A palladium‐catalyzed intramolecular α‐arylation of an amide in the presence of a bulky chiral N‐heterocyclic carbene ligand is the key step in the first catalytic synthesis of (3R)‐6‐chloro‐3‐(3‐chlorobenzyl)‐1,3‐dihydro‐3‐(3‐methoxyphenyl)‐2H‐indol‐2‐one ((R)‐ 5 ). This oxindole, in racemic form, had been shown previously to be an anticancer agent. (R)‐ 5 was obtained with an overall yield of 45% and with 96% enantioselectivity. 相似文献
3.
The straightforward, high‐yield synthesis and X‐ray structural analysis of the air‐stable planar‐chiral bis(ferrocenyl)carbene 1,3‐bis‐{(1R)‐1‐[(1R)‐1‐(trimethylsilyl)ferrocen‐2‐yl]ethyl}imidazol‐2‐ylidene ( 5 ) is reported. Compound 5 is obtained in four steps from the amine [(1R)‐1‐(dimethylamino)ethyl]ferrocene ( 1 ) upon diastereoselective silylation, methylation, nucleophilic substitution by imidazole, and deprotonation. The X‐ray crystal structure of the free carbene shows the typical conformational features of the 1,2‐disubstituted ferrocenyl units, as found in other ferrocenyl ligands derived from 1 . 相似文献
4.
Teresa M. V. D. Pinho e Melo Clara S. B. Gomes Maria I. L. Soares Antanio M. d'A Rocha Gonsalves Jos A. Paixo Ana M. Beja Manuela Ramos Silva 《Journal of heterocyclic chemistry》2004,41(4):493-497
3‐Carbethoxy‐5‐phenyl‐5H,7H‐thiazolo[3,4‐c]oxazol‐4‐ium‐1‐olate was generated from (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazolidine‐4‐carboxylic acid and its reactivity studied. This münchnone showed low reactivity as dipole although from the reaction with dimethyl acetylenedicarboxylate the corresponding (3R)‐3‐phenyl‐17H,3H‐pyrrolo[1,2‐c]thiazole‐5,6,7‐tricarboxylate could be isolated. The thermolysis of (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazolidine‐4‐carboxylic acid in refluxing acetic anhydride led to the synthesis of N‐(1‐ethoxycarbonyl‐2‐phenylvinyl)‐2‐phenyl‐4‐thioxo‐1,3‐thiazolidine. The structure of methyl (2R,4R)‐N‐ethoxyoxalyl‐2‐phenylthiazoliddine‐4‐carboxylate was determined by X‐ray crystallography. 相似文献
5.
A series of novel 1‐[(1R)‐1‐(6‐fluoro‐1,3‐benzothiazol‐2‐yl)ethyl]‐3‐substituted phenyl ureas were synthesized by the condensation of (1R)‐1‐(6‐fluoro‐1,3‐benzothiazol‐2‐yl)ethanamine with substituted phenyl isocyanates under mild conditions. Their structures were confirmed 1H, 13C, and 19F NMR spectra, and elemental analyses. The optical activities were confirmed by optical rotation measurements. The inhibition activity of 1‐[(1R)‐1‐(6‐fluoro‐1,3‐benzothiazol‐2‐yl)ethyl]‐3‐substituted phenyl ureas to acetylcholinesterase (ACHE) and butyrylcholinesterase (BCHE) was also tested. Preliminary bioassay indicated that the target ureas displayed excellent acetylcholinesterase and butyrylcholinesterase inhibition activity. J. Heterocyclic Chem., 2011. 相似文献
6.
The hexopyranosid‐2‐ylidenemalononitrile 1 reacted with phenyl isothiocyanate in the presence of triethylamine to furnish (2R,4aR,6S,10bS)‐8‐amino‐4a,6,10,10b‐tetrahydro‐6‐methoxy‐2‐phenyl‐10‐phenylimino‐4H‐thiopyrano[3′,4′:4,5]pyrano[3,2‐d][1,3]dioxine‐7‐carbonitrile (2). Starting from 1, cyclization with sulphur and diethylamine yielded (2R,4aR,6S,9bR)‐8‐amino‐4,4a,6,9b‐tetrahydro‐6‐methoxy‐2‐phenylthieno[2′,3′:4,5]pyrano[3,2‐d][1,3]dioxine‐7‐carbonitrile (3), which could be transformed into the corresponding aminomethylenamino derivative 4 by treatment with triethyl orthoformate and ammonia. Intramolecular cyclization of 4 to yield (2R,4aR,6S,11bR)‐4,4a,6,11b‐tetrahydro‐6‐methoxy‐2‐phenyl[1,3]dioxino[4″,5″:5′,6′]pyrano[3′,4′:4,5]thieno [2,3‐d]pyrimidin‐7‐amine (5) was achieved by using NaH as base. (2R,4aR,6S,9bS)‐8‐Amino‐4a,6,9,9b‐tetrahydro‐6‐methoxy‐9‐(4‐methylphenyl‐sulfonyl)‐2‐phenyl‐4H‐[1,3]dioxino[4′,5′:5,6]pyrano[4,3‐b]pyrrole‐7‐carbonitrile (6) was prepared by treatment of compound 1 with tosylazide and triethylamine. 相似文献
7.
(R)‐2,3‐Cyclohexylideneglyceraldehyde,a Chiral Pool Synthon for the Synthesis of 2‐Azido‐1,3‐diols 下载免费PDF全文
Abdul Rouf Mushtaq A. Aga Brijesh Kumar Subhash C. Taneja 《Helvetica chimica acta》2015,98(6):823-833
A new approach was proposed for the synthesis of 2‐azido‐1,3‐diols from easily available and inexpensive chiral pool synthon (R)‐2,3‐O‐cyclohexylidene‐D ‐glyceraldehyde, through Mitsunobu azidation of 1,2‐diols. Both C(2) and C(1) azides in variable ratios were obtained in alkyl substituted diols with C(2) as the major one. 相似文献
8.
Susanne Flock Clemens Bruhn Heinrich Fink Herbert Frauenrath 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(2):o101-o103
The title enantiomorphic compounds, C16H23NO4S, have been obtained in an enantiomerically pure form by crystallization from a diastereomeric mixture either of (2S,4S)‐ and (2R,4S)‐ or of (2R,4R)‐ and (2S,4R)‐2‐tert‐butyl‐4‐methyl‐3‐(4‐tolylsulfonyl)‐1,3‐oxazolidine‐4‐carbaldehyde. These mixtures were prepared by an aziridination rearrangement process starting with (S)‐ or (R)‐2‐tert‐butyl‐5‐methyl‐4H‐1,3‐dioxine. The crystal structures indicate an envelope conformation of the oxazolidine moiety for both compounds. 相似文献
9.
Isamu Shiina Kenya Nakata Keisuke Ono Teruaki Mukaiyama 《Helvetica chimica acta》2012,95(10):1891-1911
Pyridine‐3‐carboxylic anhydride (3‐PCA) was found to function as an efficient coupling reagent for the preparation of carboxylic esters from various carboxylic acids with alcohols under mild conditions by a simple experimental procedure. This novel condensation reagent 3‐PCA was applicable not only for the synthesis of achiral carboxylic esters catalyzed by 4‐(dimethylamino)pyridine (DMAP) but also for the production of chiral carboxylic esters by the combination of chiral nucleophilic catalyst, such as tetramisole (=2,3,5,6‐tetrahydro‐6‐phenylimidazo[2,1‐b][1,3]thiazole) derivatives. An efficient kinetic resolution of racemic benzylic alcohols with achiral carboxylic acids was achieved by using 3‐PCA in the presence of (R)‐benzotetramisole ((R)‐BTM), and a variety of optically active carboxylic esters were produced with high enantiomeric excesses by this new chiral induction system without using a tertiary amine. 相似文献
10.
A highly concise and stereoselective total synthesis of (5R,7S)‐kurzilactone ( 1 ) was performed by a convergent approach by means of a Jacobsen's hydrolytic kinetic resolution, a Horner? Wadsworth? Emmons reaction for the construction of the α,β‐unsaturated δ‐lactone ring system, and a highly diastereoselective Mukaiyama aldol reaction for the introduction of the formal anti‐1,3‐diol unit (Schemes 2 and 3). 相似文献
11.
Starting from the enantiomerically pure 2H‐azirin‐3‐amines (R,S)‐ 4 and (S,S)‐ 4 , the enantiomeric, optically active 4‐benzyl‐4‐methyl‐2‐phenyl‐1,3‐thiazole‐5(4H)‐thiones (R)‐ 1 and (S)‐ 1 , respectively, have been prepared (Schemes 2 and 3). In each case, the reaction of 1 with N‐(benzylidene)[(trimethylsilyl)methyl]amine ( 2 ) in HMPA in the presence of CsF and trimethylsilyl triflate gave a mixture of four optically active spirocyclic cycloadducts (Scheme 4). Separation by preparative HPLC yielded two pure diastereoisomers, e.g., (4R,5R,9S)‐ 10 and (4R,5R,9R)‐ 10 . The regioisomeric compounds 11 were obtained as a mixture of diastereoisomers. The products were formed by a 1,3‐dipolar cycloaddition of 1 with in situ generated azomethine ylide 3 , which attacks 1 stereoselectively from the sterically less‐hindered side, i.e., with (R)‐ 1 the attack occurs from the re‐side and in the case of (S)‐ 1 from the si‐side. 相似文献
12.
MichaelJ. Dobner ErnstP. Ellmerer Stefan Schwaiger Odonchimeg Batsugkh Samdan Narantuya Michaela Stütz Hermann Stuppner 《Helvetica chimica acta》2003,86(3):733-738
Three new compounds, including a benzofuran, 1‐{(2R*,3S*)‐3‐(β‐D ‐glucopyranosyloxy)‐2,3‐dihydro‐2‐[1‐(hydroxymethyl)vinyl]‐1‐benzofuran‐5‐yl}ethanone ( 1 ), a lignan, [(2S,3R,4R)‐4‐(3,4‐dimethoxybenzyl)‐2‐(3,4‐dimethoxyphenyl)tetrahydrofuran‐3‐yl]methyl (2E)‐2‐methylbut‐2‐enoate ( 2 ), and a silphiperfolene‐type sesquiterpene, [(1S,2Z,3aS,5aS,6R,8aR)‐1,3a,4,5,5a,6,7,8‐octahydro‐1,3a,6‐trimethylcyclopenta[c]pentalen‐2‐yl]methyl acetate ( 3 ), together with the known coumarins obliquin ( 4 ) and its 5‐methoxy derivative 5 were isolated from the roots of Leontopodium alpinum. Another known coumarin derivative, 5‐hydroxyobliquin ( 6 ), was isolated from the roots of L. leontopodioides. The structures of these compounds were established by spectroscopic studies. 相似文献
13.
Amal Feddouli Moulay Youssef Ait Itto Aïssa Hasnaoui Didier Villemin Paul‐Alain Jaffrs Jana Sopkova‐De Oliveira Santos Abdelkhalek Riahi FranOis Huet Jean‐Claude Daran 《Journal of heterocyclic chemistry》2004,41(5):731-735
Herein we report an efficient one pot synthesis of new chiral 4,5‐dihydro‐4‐arylspiro[1,3,4‐thiadiazole]‐5,2′‐camphane‐2‐carboxylic acid ethyl esters 5–7 and 4,5‐dihydro‐3‐arylspiro[1,4,2‐oxathiazole]‐5,2′‐camphane 11–13 , using 1,3‐dipolar cycloaddition of nitrilimines 2–4 and nitrile oxides 8–10 to (1R)‐thiocamphor 1 respectively. The structure of the newly prepared 1,3,4‐thiadiazoles 5–7 (obtained as pure diastereoisomers) were fully established via spectroscopic analysis and X‐ray structural analysis which proved the absolute configuration of the C5 spiranic carbon to be (R). NMR spectral analysis were also very useful to show the new 1,4,2‐oxathiazoles 11–13 are mixtures of two (5R)/(5S) diastereoisomers with the ratio 6:4,7:3 and 6:4 respectively. 相似文献
14.
Charles Fehr Dr. Oliver Knopff Dr. Jean‐Yves de Saint Laumer Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(8):2487-2495
(+)‐(R,Z)‐5‐Muscenone ((R)‐ 1 ) was synthesized by an enantioselective aldol reaction, catalyzed by new ephedrine‐type Ti reagents (up to 70 % enantiomeric excess). Substrate‐directed diastereoselective reduction of the aldol product and Grob fragmentation of the tosylate of the resultant 1,3‐diol afforded (+)‐ 1 . This approach also gave access to (?)‐(R,E)‐5‐muscenone and (?)‐(R)‐muscone. 相似文献
15.
Stereocontrolled Synthesis of syn‐β‐Hydroxy‐α‐Amino Acids by Direct Aldolization of Pseudoephenamine Glycinamide 下载免费PDF全文
Dr. Ian B. Seiple Jaron A. M. Mercer Robin J. Sussman Ziyang Zhang Prof. Dr. Andrew G. Myers 《Angewandte Chemie (International ed. in English)》2014,53(18):4642-4647
β‐Hydroxy‐α‐amino acids figure prominently as chiral building blocks in chemical synthesis and serve as precursors to numerous important medicines. Reported herein is a method for the synthesis of β‐hydroxy‐α‐amino acid derivatives by aldolization of pseudoephenamine glycinamide, which can be prepared from pseudoephenamine in a one‐flask protocol. Enolization of (R,R)‐ or (S,S)‐pseudoephenamine glycinamide with lithium hexamethyldisilazide in the presence of LiCl followed by addition of an aldehyde or ketone substrate affords aldol addition products that are stereochemically homologous with L ‐ or D ‐threonine, respectively. These products, which are typically solids, can be obtained in stereoisomerically pure form in yields of 55–98 %, and are readily transformed into β‐hydroxy‐α‐amino acids by mild hydrolysis or into 2‐amino‐1,3‐diols by reduction with sodium borohydride. This new chemistry greatly facilitates the construction of novel antibiotics of several different classes. 相似文献
16.
Novel and Stereospecific Synthesis of (2S)‐3‐(2,4,5‐Trifluorophenyl)propane‐1,2‐diol from D‐Mannitol 下载免费PDF全文
Derya Aktaş Meryem Fıstıkçı Özlem Gündoğdu Hasan Seçen M. Fethi Şahin Ramazan Altundaş Yunus Kara 《Helvetica chimica acta》2015,98(8):1127-1131
A stereospecific synthesis of (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol from D ‐mannitol has been developed. The reaction of 2,3‐O‐isopropylidene‐D ‐glyceraldehyde with 2,4,5‐trifluorophenylmagnesium bromide gave [(4R)‐2,2‐dimethyl‐1,3‐dioxolan‐4‐yl](2,4,5‐trifluorophenyl)methanol in 65% yield as a mixture of diastereoisomers (1 : 1). The Ph3P catalyzed reaction of the latter with C2Cl6 followed by reduction with Pd/C‐catalyzed hydrogenation gave (2S)‐3‐(2,4,5‐trifluorophenyl)propane‐1,2‐diol with >99% ee and 65% yield. 相似文献
17.
Sergej Malaschichin Changchun Fu Anthony Linden Heinz Heimgartner 《Helvetica chimica acta》2005,88(12):3253-3262
The reactions of 1,3‐dioxolane‐2‐thione ( 3 ) with (S)‐2‐methyloxirane ((S)‐ 1 ) and with (R)‐2‐phenyloxirane ((R)‐ 2 ) in the presence of SiO2 in anhydrous dichloroalkanes led to the optically active spirocyclic 1,3‐oxathiolanes 8 with Me at C(7) and 9 with Ph at C(8), respectively (Schemes 2 and 3). The analogous reaction of 1,3‐dimethylimidazolidine‐2‐thione ( 4a ) with (R)‐ 2 yielded stereoselectively (S)‐2‐phenylthiirane ((S)‐ 10 ) in 83% yield and 97% ee together with 1,3‐dimethylimidazolidin‐2‐one ( 11a ). In the cases of 3‐phenyloxazolidine‐2‐thione ( 4b ) and 3‐phenylthiazolidine‐2‐thione ( 4c ), the reaction with (RS)‐ 2 yielded the racemic thiirane (RS)‐ 10 , and the corresponding carbonyl compounds 11b and 11c (Scheme 4 and Table 1). The analogous reaction of 4a with 1,2‐epoxycyclohexane (= 7‐oxabicyclo[4.1.0]heptane; 7 ) afforded thiirane 12 and the corresponding carbonyl compound 11a (Scheme 5). On the other hand, the BF3‐catalyzed reaction of imidazolidine‐2‐thione ( 5 ) with (RS)‐ 2 yielded the imidazolidine‐2‐thione derivative 13 almost quantitatively (Scheme 6). In a refluxing xylene solution, 1,3‐diacetylimidazolidine‐2‐thione ( 6 ) and (RS)‐ 2 reacted to give two imidazolidine‐2‐thione derivatives, 13 and 14 (Scheme 7). The structures of 13 and 14 were established by X‐ray crystallography (Fig.). 相似文献
18.
Wieland Tyrra Harald Scherer Lesya A. Babadzhanova Natalya V. Kirij Yurii L. Yagupolskii Dieter Naumann Ingo Pantenburg 《Helvetica chimica acta》2008,91(1):97-110
A convenient synthesis of the 1,3‐dihydro‐1,3,3‐tris(perfluoroalkyl)isobenzofuran‐1‐ols 3a , b was elaborated starting from commercially available phthaloyl dichloride and trimethyl(perfluoroalkyl)silanes (Me3SiRf) 1a , b (Rf=CF3, C2F5) in the presence of a fluoride source (Schemes 1 and 3). In a reaction analogous to alkyl Grignard reagents, double chloride substitution by two perfluoroalkyl groups and subsequent addition of one perfluoroalkyl group with concomitant ring closure led to this new class of compounds (Scheme 2). The syntheses of the alcohols and some alcoholates, as well as of the corresponding trimethylsilyl ethers are described. A combination of special 1D and 2D NMR experiments allowed the assignment of all atoms of the new compounds. The solid‐state structure of 1,3‐dihydro‐1,3,3‐tris(trifluoromethyl)isobenzofuran‐1‐ol ( 3a ) was elucidated by X‐ray diffraction methods. 相似文献
19.
Atsushi Sudo Long‐Chao Du Shoji Hirayama Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2010,48(13):2777-2782
Thermally induced polymerizations of a series of 1,3‐benzoxazines with a variety of substituents on the nitrogen atom were investigated in detail, particularly in the following three aspects of the polymerization: (1) N‐alkyl‐1,3‐benzoxazines are much more reactive than N‐phenyl‐1,3‐benzoxazine. (2) The polymerization rate depended on the bulkiness of the N‐substituent. The bulkier the substituent was, the slower the polymerization was. (3) The polymerizations accompanied weight loss due to the elimination of the corresponding imine (R‐N = CH2), and its extent became larger when R was more bulky. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2777–2782, 2010 相似文献
20.
The Ti(TADDOLato) complexes dichloro[(4R,5R)‐2,2‐dimethyl‐α,α,α′,α′‐tetraphenyl‐1,3‐dioxolane‐4,5‐dimethanolato(2−)‐O,O′]titanium ((R)‐ 1a ) and dichloro[(4R,5R)‐2,2‐dimethyl‐α,α,α′,α′‐tetra(naphthalen‐1‐yl)‐1,3‐dioxolane‐4,5‐dimethanolato(2−)‐O,O′]titanium ((R)‐ 1b ) are efficient catalysts for the electrophilic enantioselective chlorination and bromination of β‐keto esters with N‐chlorosuccinimide (NCS) and N‐bromosuccinimide (NBS), respectively. With 5 mol‐% of catalyst at room temperature an enantioselectivity of up to 88% ee could be obtained for the chlorination reaction. Under comparable conditions, bromination reactions are slower and less stereoselective. 相似文献