共查询到20条相似文献,搜索用时 15 毫秒
1.
Om V SinghHyunsoo Han 《Tetrahedron letters》2003,44(11):2387-2391
A general methodology for the stereoselective synthesis of 1-deoxymannojirimycin and its three other stereoisomers is described. The achiral olefin 6 was converted through the common olefin intermediate 12 to the target compounds in a highly stereocontrolled manner. The regioselective asymmetric aminohydroxylation (AA) and diastereoselective dihydroxylation reactions were used for the introduction of all four stereocenters in the targets, and the ring-closing metathesis (RCM) reaction was utilized for the construction of the required six-membered ring. 相似文献
2.
Hyunsoo Han 《Tetrahedron letters》2003,44(8):1567-1569
A new general methodology for the asymmetric synthesis of polyhydroxypiperidines is described. The readily available achiral olefin 4 was transformed to 5-des(hydroxymethyl)-1-deoxynojirimycin (1) and its mannose analog 10 via regioselective aminohydroxylation (AA), ring-closing metathesis (RCM), and diastereoselective dihydroxylation reactions. Thus, the developed methodology made it possible to install all stereocenters in 1 and 10 in a highly stereocontrolled fashion. 相似文献
3.
An efficient diastereoselective synthesis of 5-substituted (2-thioxo-oxazolidin-4-yl)phosphonic acid diethyl esters from metallated diethyl isothiocyanomethylphosphonate and aldehydes has been developed. The three-step transformation of oxazolidine-2-thione derivatives into N-Boc 1-amino-2-hydroxyalkylphosphonic acid diethyl esters is also described. 相似文献
4.
The interaction of 2-amino-1,3,4-oxadiazole-5-carboxamidoxime with nitriles in the presence of ZnCl2 and HCl or with trichloroacetic anhydride affords 2-amino-5-(5R-1,2,4-oxadiazolyl-3)-1,3,4-oxadiazoles. Their reactions with N-nucleophiles have been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2100–2103, December, 1993. 相似文献
5.
G. E. Camí E. E. Chufn J. C. Pedregosa E. L. Varetti 《Journal of Molecular Structure》2001,570(1-3):119-127
The infrared and Raman spectra in the range 4000–50 cm−1 were obtained for 5-amino-1,3,4-thiadiazole-2-sulfonamide. The molecular geometry was optimized by means of the DFT methods of quantum chemistry (B3LYP/6-31G**), resulting in a structure which agrees quite well with that obtained by X-ray diffraction. The wavenumbers corresponding to the normal modes of vibration were calculated using the same approximation and the associated force field converted to a set of local symmetry coordinates, with subsequent calculation of the potential energy distribution. An assignment of the observed bands is proposed on the basis of such calculations and the comparison with related molecules. 相似文献
6.
S. S. Shukurov M. A. Kukaniev I. M. Nasyrov K. S. Zakharov R. A. Karakhanov 《Russian Chemical Bulletin》1993,42(11):1871-1874
The reactions of 2-amino-5-mercapto-(or 2,5-dimercapto)-1,3,4-thiadiazoles with 2-bromo-7-methyl-5-oxo-5H-1, 3,4-thiadiazolo[3, 2-a]pyrimidine to give the corresponding sulfides have been studied. The possibility of S-alkylation and addition of quinone at the free mercapto group in the 1,3,4-thiadiazole ring has been shown. The reactions at the amino group with benzoyl chloride and chloroformates have been investigated. The conditions of cyciodehydration at the amino group with ethyl acetoacetate and bromination of the pyrimidine fragment of 7-methyl-5-oxo-5H-1,3,4-thiadiazolo[3,2-a]pyrimidine have been found.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1954–1957, November, 1993 相似文献
7.
In this study, we synthesized a new series of substituted aliphatic 1,3,4-thiadiazol-2(3H)-one derivatives (6-24) in yields ranging from 42 to 70% with an interesting mechanism that involves internal nucleophilic substitution followed by an SN2-type nucleophilic substitution. First, 1-(4-chlorophenyl)-2-((5-methyl-1,3,4-thiadiazol-2-yl)thio)ethanone (3) was synthesized from the reaction of 5-methyl-1,3,4-thiadiazole-2-thiol (1) with 2-bromo-1-(4-chlorophenyl)ethanone (2) in the presence of potassium hydroxide. Then, 1-(4-chlorophenyl)-2-((5-methyl-1,3,4-thiadiazol-2-yl)thio)ethanol (4) was synthesized by a reduction reaction of this compound using NaBH4. Finally, 5-methyl-3-alkyl-1,3,4-thiadiazol-2(3H)-one derivatives (6-24), which are the target compounds, were synthesized from the reaction of this compound (4), which is a secondary alcohol with various alkyl halides (5a-n) in the presence of sodium hydride (NaH). This study presents an interesting reaction mechanism related to the synthesis of aliphatic 1,3,4-thiadiazol-2(3H)-one derivatives that is not recorded in the literature. 相似文献
8.
Robert L. Broadrup 《Tetrahedron》2005,61(43):10277-10284
A selection of azapeptidomimetics containing constraining lactam rings have been prepared by Mitsunobu cyclization of serine/homologated serine-azaalanine derivatives. These include sterically-congested β-lactams, as well as γ-butyrolactam and δ-valerolactam analogs. A novel azaamino acid acylation method was developed to prepare the sterically demanding α-benzyl-serine-azaalanine precursor. In all cases, the Mitsunobu conditions were highly efficient in forming the desired azapeptidomimetic lactams. The reported process represents a general strategy for the synthesis of peptidomimetic structures with a constraining lactam ring. 相似文献
9.
10.
M. A. Pudovik L. K. Kibardina R. Kh. Al'myanova R. M. Kamalov A. N. Pudovik 《Russian Chemical Bulletin》1996,45(7):1769-1770
The reactions ofO-phenyl chloromethylisothiocyanatothioxophosphonate andO-phenyl chloromethylisocyanatophosphonate with trimethylsilyldiethylamine lead to the formation of 1,3,4-thiazaphosphol-2-ine and 1,3,4-oxazaphosphol-2-ine, respectively. Phosphorylation ofN-methyl-N-phenyl-N,N-bis(trimethylsilyl)urea withO-phenyl chloromethylchlorophos phonate gives 1,3,4-diazaphospholidin-2-one.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1857–1859, July, 1996. 相似文献
11.
Compounds described previously as 2-amino-5-aryl-5H-thiazolo[4,3-b]-1,3,4-thiadiazoles were found to be thiosemicarbazones of aromatic aldehydes.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya No. 6, pp. 1228–1229, June, 1997. 相似文献
12.
Kim L. Curtis 《Tetrahedron letters》2005,46(32):5297-5300
The novel (2S,3S,4R)-3-amino-2-hydroxymethyl-4-hydroxypyrrolidine 5 has been produced in an efficient synthesis from trans-4-hydroxy-l-proline 8. The key step involves a tethered aminohydroxylation of the alkene 7 to introduce regio- and stereoselectively the amino alcohol functionality in the resulting products 6 and 13. Subsequent deprotection steps furnish the target molecule 5 as well as several differentially protected analogues. 相似文献
13.
A concise and efficient synthesis of 2,3-dihydro-1H-isoindol-1-ones based upon the Parham-type cyclization of iodinated benzyldicarbamates is reported. The synthetic potential of this approach was further emphasized by the assembly of the polycyclic framework of vitedoamine A. 相似文献
14.
Agnieszka Kudelko 《Tetrahedron》2011,67(44):8502-8508
Reactions of symmetrical 1,1′-diphenylthiodiacetic acid dihydrazide and triethyl orthoesters in the presence of catalytic amount of glacial acetic acid resulted in the formation of three heterocyclic products: the appropriate bis(1,3,4-oxadiazol-2-yl-phenylmethyl) sulfides, 2-benzyl-1,3,4-oxadiazoles and 2-benzoyl-1,3,4-oxadiazoles. The presence of the latter two compounds is connected with carbon-sulfur fission in the molecule of the starting hydrazide. The identity of the unexpected fission products was confirmed by parallel syntheses of the model 1,3,4-oxadiazoles from phenylacetic acid hydrazide and 2-hydroxymethyl-1,3,4-oxadiazole derivatives. 相似文献
15.
Trost BM Pissot-Soldermann C Chen I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(3):951-959
The interesting biological properties of the hamigerans wherein hamigeran B is a potent antiviral agent with low cytotoxicity to host cells make these deceptively simple looking structures challenging synthetic targets. A strategy to hamigeran B evolved wherein the three contiguous stereocenters are established ultimately from a Pd catalyzed asymmetric allylic alkylation (AAA). The latter involves an asymmetric allylation of a non-stabilized ketone enolate in 77 % yield and 93 % ee. By using this process, (S)-5-allyl-2-isopropyl-5-methyl-1-trifluoromethanesulfonyloxycyclopentene becomes available in four steps from 2-methylcyclopentanone. Introduction of the aryl unit by cross-coupling proceeded intermolecularly but failed intramolecularly. On the other hand, reductive removal of the triflate permitted a Heck reaction to effect intramolecular introduction of the aryl ring. The unusual conformational properties of this molecular architecture are revealed by the regioselectivity of the beta-hydrogen elimination in the Heck reaction and the diastereoselectivity of the reduction establishing the stereochemistry of the carbon bearing the isopropyl group. The successful route consists of 15 steps from 2-methylcyclopentanone and dimethylorcinol illustrating the efficiency of the route based upon the Pd AAA. 相似文献
16.
Bi-functional dendritic building blocks for convergent dendrimer growth were successfully synthesized from phenolic templates in the solid phase via a Mitsunobu reaction. Each arm of the dendron building block carries an orthogonally protected secondary amine along the arm, and a peripheral primary amine or phenol group (building block type 1) or a tertiary amine junction with orthogonally protected peripheral primary amine or carboxyl groups (building block type 2). The synthetic routes reported in this work are general and applicable for the preparation of diverse building blocks, controlling protection, arm length, and peripheral moieties. These novel dendron units can form unusual dendritic architectures by solid-phase chemistry, which may be incorporated into specific complex structures expanding the scope of dendrimer science. 相似文献
17.
以2-氨基-5-巯基-1,3,4-噻二唑和氯乙酸乙酯为原料,水相快速合成中间体(5-氨基-1,3,4-噻二唑-2-基)硫乙酸乙酯,该中间体再与芳氧乙酰氯反应,高产率得到6种目标化合物[5-(芳氧乙酰氨基)-1,3,4-噻二唑-2-基]硫乙酸乙酯(5a-5f)。所有这些化合物都经过了红外、元素分析以及核磁共振氢谱的表征。采用离体平皿法对目标化合物进行了除草活性试验,部分化合物显示出良好的除草活性,而小麦对其耐受。 相似文献
18.
Equimolar mixtures of aromatic aldehydes with thioglycolic acid and thiosemicarbazide in H2SO4 transform into 2-amino-5-aryl-5H-thiazolo[4,3-b]-1,3,4-thiadiazoles.Translated fromIzvestiya Akademioi Nauk. Seriya Khimicheskaya, No. 3, pp. 763–764, March, 1996. 相似文献
19.
Satyendra Kumar Pandey 《Tetrahedron letters》2008,49(20):3297-3299
A short synthesis of the nonproteinogenic amino acid, (2S,4R)-4-hydroxyornithine is described. Starting from racemic benzyl glycidol, the scaffold of the target compound was constructed in high enantio- and diastereoselectivity using Jacobsen’s hydrolytic kinetic resolution (HKR) and regioselective opening of an epoxide as key steps. 相似文献