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1.
Satwinder Singh 《Tetrahedron letters》2004,45(33):6349-6352
Epoxidation of the allylic alcohols 10 and 11 using the VO(acac)2/t-BuOOH system followed by an intramolecular 5-exo cyclization of the resulting δ-epoxycarbamates 12, 13, 18, and 19 has been shown to provide a general and efficient solution for the asymmetric synthesis of polyhydroxy pyrrolidines. The requisite vicinal amino alcohol functionality was enantio-/regio-selectively installed by the Os-catalyzed asymmetric aminohydroxylation reaction of the designed achiral olefin 6. 相似文献
2.
A new synthesis for (+)-casuarine (1) and its 6,7-diepi isomer (15) in a stereocontrolled manner, is reported herein. An appropriately protected polyhydroxylated pyrrolidine, such as (2R,3R,4R,5R)-3,4-dibenzyloxy-2′-O-tert-butyldiphenylsilyl-2,5-bis(hydroxymethyl)pyrrolidine (3, protected DMDP), easily available from d-fructose, was chosen as the chiral starting material. Compounds 1 and 15 were obtained from 3, in seven steps, in a 23.2 and 20.5% overall yields, respectively. 相似文献
3.
The stereoselective synthesis of two epimeric penta-hydroxylated indolizidines was accomplished from 2,3:5,6-di-O-isopropylidene-α-d-mannofuranose and N-(2-methylpent-4-en-2-yl)hydroxylamine. The transformation of these substrates into the corresponding 7-oxa-1-azabicyclo[2.2.1]heptane by the intramolecular 1,3-dipolar cycloaddition was the key step of the synthesis. The adduct was transformed into the tricyclic ammonium salt by intramolecular N-alkylation. The tricyclic ammonium salt was converted to the target compounds by: (route 1) the catalytic hydrogenation; or (route 2) the reaction with sodium azide, followed by the enantioselective reduction of the resulting indolizidinone. 相似文献
4.
The specimens for previous studies on the secondary metabolites of the Formosan octocoral Isis hippuris were all collected at Green Island. In the course of our studies on bioactive compounds from marine organisms, the acetone-solubles of the Formosan octocoral I. hippuris collected at Orchid Island has led to the isolation of six new polyoxygenated steroids (1-6), along with a known compound 7. Compound 6 possesses a new type of steroid side chain moiety. The structures of these compounds were determined on the basis of their spectroscopic and physical data. The anti-HCMV (human cytomegalovirus) activity and cytotoxicity against selected cell lines of 1-7 were evaluated. Compound 3 exhibited inhibitory activity against HCMV, with an EC50 values of 2.0 μg/mL, respectively. Compound 7 displayed cytotoxicity against P-388 and A-549 cell lines with ED50 values of 3.2 and 3.86 μg/mL, respectively. 相似文献
5.
A concise synthetic pathway towards 5-substituted indolizidines 总被引:1,自引:0,他引:1
The total synthesis of 5-(2′-hydroxyethyl)indolizidine via 5-thioindolizidinone is described. The key step is the transformation of 5-thioindolizidinone via Eschenmoser’s sulfide contraction. The racemic mixture of 5R,9R- and 5S,9S-5-(2′-hydroxyethyl)indolizidine was obtained in seven steps in 17% overall yield from 2-allyl cyclopentanone. 相似文献
6.
Gao-Feng Shi 《Tetrahedron》2008,64(22):5005-5012
The concise and divergent total syntheses of (−)-swainsonine, (−)-7-alkyl swainsonines, and (−)-2,8a-diepilentiginosine from a common chiral heterocyclic enaminoester intermediate in five-step sequences are presented. The highly efficient annulation reaction of the chiral heterocyclic enaminoester with various α,β-unsaturated carboxylates, and a straightforward carboxy inversion constituted the key features of the synthetic pathway. This work provides an example for divergent synthesis of different natural and unnatural polyhydroxylated indolizidines from a readily available platform. 相似文献
7.
Photooxygenation of Furylalkylamines: Easy Access to Pyrrolizidine and Indolizidine Scaffolds
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Dr. Dimitris Kalaitzakis Myron Triantafyllakis Manolis Sofiadis Dr. Dimitris Noutsias Prof. Dr. Georgios Vassilikogiannakis 《Angewandte Chemie (International ed. in English)》2016,55(14):4605-4609
A highly adaptable method targeting the ubiquitous and very important pyrrolizidine and indolizidine scaffolds is presented. The general synthetic utility of the method is underscored by its application to the rapid and easy synthesis of five natural products starting from readily accessible alkylfuran precursors. These unprotected primary furylalkylamines are subjected to photooxygenation conditions, which initiate a complex cascade reaction sequence concluding with the production of high value motifs. This sequence can be tailored to need by varying the choice of both photosensitizer and base additive. 相似文献
8.
9.
De novo synthesis of noncompetitive glycosidase inhibitors l-gulo-DNJ and l-talo-DNJ has been achieved in 9-10 steps starting from Garner’s aldehyde. Key to the success of this procedure was the construction of the 2,3-unsaturated piperidine 14, which syn dihydroxylation under Kishi’s and Donohoe’s conditions led to the desired iminosugars. 相似文献
10.
Wenjian Wu Xingrong Zeng Hongqiang Li Xuejun Lai Zengyang Yan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):229-239
Polyhydroxylated polybutadiene (PHPB) was synthesized via a thiol-ene click reaction between hydroxyl-terminated polybutadiene (HTPB) and 2-mercaptoethanol (ME) with 2,2’-azoisobutyronitrile (AIBN) as initiator. Effects of AIBN content, reaction time and temperature on the click reaction were investigated by determining hydroxyl value of the PHPB. The PHPB was characterized by FT-IR, 1H-NMR, 13C-NMR and GPC. Relative reactivity of three types of C?C double bonds (1,2-vinyl, 1,4-cis and 1,4-trans units) in the HTPB reacting with the ME was discussed. The results showed that the optimal reaction conditions were that the AIBN content, reaction time and temperature were 2.0 wt%, 180 min and 70°C, respectively. Under these conditions, the hydroxyl value of the PHPB was 3.12 mmol·g?1 when the HTPB/ME mass ratio was 10:2. All three types of C?C double bonds in the HTPB could react with the ME and the reactivity order was: 1,2-vinyl unit > 1,4-cis unit > 1,4-trans unit. 相似文献