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1.
Ângelo de FátimaRonaldo Aloise Pilli 《Tetrahedron letters》2003,44(48):8721-8724
The total syntheses of (R)-argentilactone (five steps, 25% overall yield) and (R)-goniothalamin (three steps, 61% overall yield) have been described through the enantioselective catalytic allylation of aldehydes (including a propargylic aldehyde) which provided a rapid access to these natural products that display very interesting biological activities. 相似文献
2.
Biotransformation of (+)-(1R,2S)-fenchol by the larvae of Spodoptera litura was carried out. Substrate was converted to three new terpenoids, (+)-(1R,2S)-10-hydroxyfenchol, (+)-(1R,2R,3S)-8-hydroxyfenchol and (−)-(1S,2S,6S)-6-exo-hydroxyfenchol, and one known terpenoid, (−)-(1R,2R,3R)-9-hydroxyfenchol. These structures were established by NMR, IR, specific rotation and mass spectral studies. 相似文献
3.
Kenji Mori 《Tetrahedron》2009,65(14):2798-699
All of the stereoisomers of the components of the female-produced sex pheromone of a moth, Lyclene dharma dharma, were synthesized. They are (R)- and (S)-6-methyl-2-octadecanone, (6R,14R)-, (6R,14S)-, (6S,14R)-, and (6S,14S)-6,14-dimethyl-2-octadecanone, and (R)- and (S)-14-methyl-2-octadecanone. Enantiomers of citronellal and methyl (S)-3-hydroxy-2-methylpropanoate were the starting materials, and olefin cross metathesis was employed as the key reaction. 相似文献
4.
Takeshi Yamamoto Hideo UjiharaShinya Watanabe Makoto HaradaHiroyuki Matsuda Toshimitsu Hagiwara 《Tetrahedron》2003,59(4):517-524
The synthesis characterized by cationic olefin cyclizations accomplished using ketone enol esters and odor of novel (1R,6S)- and (1S,6R)-2,2,6-trimethylcyclohexyl methyl ketones (5) are described. The stereoselective syntheses of (E)-(1R,6S)- and (E)-(1S,6R)-1-(2,2,6-trimethylcyclohexyl)-2-buten-1-one (6) and (1R,6S)-ethyl 2,2,6-trimethylcyclohexylcarboxylate (7), useful raw materials for flavor and fragrance, starting from the (1R,6S)- and (1S,6R)-5 are also described. 相似文献
5.
Tetrahydroisoquinoline alkaloids, (S)-(−)-trolline, (R)-(+)-crispin A, and (R)-(+)-oleracein E, have been synthesized stereoselectively from the both enantiomers of common intermediate (S)-4 and (R)-4. The key step in the synthesis include a stereoselective Bi(OTf)3-catalyzed intramolecular 1,3-chirality transfer reaction of chiral non-racemic amino allylic alcohols (S)-6 and (R)-6 to construct both enantiomers of (E)-1-propenyl tetrahydroisoquinoline 4. 相似文献
6.
T. M. Ugurchieva A. V. Lozanova M. V. Zlokazov V. V. Veselovsky 《Russian Chemical Bulletin》2007,56(8):1544-1549
trans-Stereoselective electrophilic cyclization of (2R*,SS*)-N, N-diisopropyl-2-phenylsulfinylpent-4-enamide under the action of bromine afforded (3R*,5S*, SS*)-N-(5-bromomethyl-3-phenylsulfinyltetrahydrofuran-2-ylidene)-N,N-diisopropylammonium bromide. Its transformations under the conditions of hydrolysis, dehydrobromination, and hydride reduction
were studied.
Dedicated to Academician V. A. Tartakovsky on the occasion of his 75th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1485–1490, August, 2007. 相似文献
7.
A novel dichloro zinc complex (L1)ZnCl2, where L1 is N,N′-bis-(2,6-dichloro-benzyl)-(R,R)-1,2-diaminocyclohexane, has been synthesized and characterized. The dimethyl derivatives, generated in situ from the well characterized dichloro zinc complexes (L1)ZnCl2 and (L2)ZnCl2, where L2 is N,N′-bis-(benzyl)-(R,R)-1,2-diaminocyclohexane, were employed as initiators for the ring opening polymerization (ROP) of rac-lactide (rac-LA). The complexes were found to be highly efficient initiators yielding the polylactide (PLA) with a narrow molecular weight distribution. The catalytic activity and heterotactic selectivity of the Zn(II) complexes were affected by the substituents on the phenyl groups of benzyl moieties in (R,R)-1,2-diaminocyclohexane. The dimethyl derivative of (L2)ZnCl2 produced highly stereocontrolled PLA with Pr = 0.75 at −25 °C. 相似文献
8.
Yoko Kameda 《Tetrahedron》2006,62(41):9751-9757
(4R,8R)-4,8-Dimethyldecanal, a common aggregation pheromone of Tribolium flour beetles, has been synthesized from (R)-2,3-O-isopropylideneglyceraldehyde in 11 steps and 7% overall yield. The key step in the synthesis is the highly diastereoselective chelation-controlled radical reaction of ethyl (4S,5R)-4-benzyloxy-5,6-(isopropylidenedioxy)-2-methylenehexanoate with ethyl (R)-5-iodo-3-methylpentanoate performed in the presence of 7 equiv of MgBr2·OEt2. 相似文献
9.
Akira Sakakura Kazufumi Shioya Hirotaka Katsuzaki Toshikatsu Imamura Kunio Imai 《Tetrahedron》2009,65(34):6822-6827
The entomogenous ‘Hanasanagitake’ mushroom, Isaria japonica, is used as a folk medicine and as a traditional health food choice in Japan. A search for naturally occurring antioxidative compounds from the mushroom led to the isolation of a novel pseudo-di-peptide, named Hanasanagin, and a possible biogenetic precursor. The structures of the pseudo-di-peptides were determined as (R)-3,4-diguanidinobutanoyl-(S)-DOPA and (R)-3,4-diguanidinobutanoyl-(S)-tyrosine by spectral analysis, chemical synthesis and enzymatic conversion. 相似文献
10.
Kazuishi Makino 《Tetrahedron letters》2005,46(47):8159-8162
(2S,3R)-3-Hydroxy-3-methylproline, a constituent of cyclodepsipeptides polyoxypeptins A and B, was efficiently synthesized by lithium chloride-induced diastereoselective tandem Michael-aldol reaction using methyl vinyl ketone and N-1-naphthylsulfonylglycine (R)-binaphthyl ester and subsequent hydrolysis of the product in 39% overall yield and five steps. 相似文献
11.
Enantioselective oxodiene Diels-Alder reactions catalyzed by (1R,2R)-DPEN-derived triazolium salts were realized successfully. With 0.5 mol % of (1R,2R)-DPEN-derived triazolium salt C and 150 mol % of Et3N, the reactions of various α-chloroaldehydes (α-bromoaldehyde) with substituted enones led to 3,4-dihydropyridinones and their derivatives in good yields, diastereoselectivities, and enantioselectivities (up to 97% ee). 相似文献
12.
Nermeen A. Eltahawy Amany K. Ibrahim Mohamed M. Radwan Mahmoud A. ElSohly Hashim A. Hassanean Safwat A. Ahmed 《Tetrahedron letters》2014
Chemical investigation of the Red Sea soft coral Sarcophyton auritum led to the isolation and structure elucidation of two new diterpene cembranoids; 2-epi-sarcophine (2) and (1R,2E,4S,6E,8R,11R,12R)-2,6-cembradiene-4,8,11,12-tetrol (4), as well as two known diterpene cembranoids, reported for the first time from this species, namely sarcophine (1) and (+)-7α,8β-dihydroxydeepoxysarcophine (3). Structure elucidation was achieved using spectroscopic techniques, including 1D and 2D NMR and HRMS. The isolated cembranoids were found to display high cytotoxicity against HepG2 (liver cancer cell line) and MCF-7 (breast cancer cell line). 相似文献
13.
Ken-ichi Toyama 《Tetrahedron letters》2006,47(40):7163-7166
We have developed a chemoenzymatic synthesis of (R)-thiolactomycin (1) having a chiral quaternary carbon atom at C5. In the kinetic resolution of the thiotetronic acid precursor 4, both enantiomers were obtained with high enantiomeric excess by use of Chirazyme® L-2. Chemical transformations of the (R)-alcohol 4 provided the chiral (R)-thiolactomycin (1) in 36% yield in five steps. 相似文献
14.
Kunihiko Takabe Masataka Sugiura Yuya Asumi Nobuyuki Mase Hidemi Yoda Hiroyasu Shimizu 《Tetrahedron letters》2005,46(20):3457-3460
A simple and practical synthesis of (R)-(−)-muscone was achieved by optical resolution of dl-muscone using tartaric acid derivatives. The acetalization of dl-muscone with N,N′-dibenzyl-l-tartaramide in the presence of Sc(OTf)3 and methyl orthoformate furnished a diastereomeric mixture of acetals, which were readily separated by simple recrystallization. Diastereomerically pure acetal was hydrolyzed to give optically pure muscone and recovered N,N′-dibenzyl-l-tartaramide. 相似文献
15.
R. Sateesh Chandra KumarG. Venkateswar Reddy K. Suresh BabuJ. Madhusudana Rao 《Tetrahedron letters》2011,52(34):4382-4384
A highly stereoselective total synthesis of (+)-(8R,8aR)-perhydro-8-indolizidinol is described. Key steps involved in this synthesis are diastereoselective zinc allylation, azido-olefin cyclization and reductive amination followed by cyclization which effectively constructed the indolizidine ring. This contributes a unique approach to the synthesis of indolizidine alkaloids that offers the advantages of brevity and relatively high overall yields. 相似文献
16.
Nicholas M Shaw 《Tetrahedron》2004,60(3):747-752
The substrate specificity of the heat-stable stereospecific amidase from Klebsiella oxytoca was investigated. In addition to the original substrate, 3,3,3-trifluoro-2-hydroxy-2-methylpropanamide, the amidase accepted 2-hydroxy-2-(trifluoromethyl)-butanamide and 3,3,3-trifluoro-2-amino-2-methylpropanamide as substrates. Compounds with larger side chains and compounds where the hydroxyl group was substituted with a methoxy group, or in which the CF3 group was substituted by CCl3, were not accepted. The biotransformation is a new synthetic route to (R)-(+)-3,3,3-trifluoro-2-amino-2-methylpropanoic acid, and its related (S)-(−)-amide, and to (R)-(+)-2-hydroxy-2-(trifluoromethyl)-butanoic acid and its related (S)-(−)-amide. 相似文献
17.
The concise synthesis of (8aR)-(−)-albaconol (1) from (8aR)-albicanol (2) obtained from the lipase-assisted asymmetric acetylation of rac-2, was achieved in 45% overall yield (eight steps). By comparison of the sign of specific rotation of between synthetic (8aR)-(−)-albaconol (1) and natural (+)-albaconol (1), the absolute structure of natural (+)-1 was determined to be 1R,2R,4aS,8aS configuration. 相似文献
18.
Bruno A. Figadère J. Steven McElfresh Kent M. Daane Jocelyn G. Millar 《Tetrahedron letters》2007,48(48):8434-8437
Headspace volatiles of virgin female grape mealybugs contained a single compound that elicitited responses from antennae of males in GC-electroantennogram analyses. The structure, identified as (R∗,R∗)-trans-(3,4,5,5-tetramethylcyclopent-2-en-1-yl)methyl 2-methylpropanoate, an irregular, non-head-to-tail monoterpenoid, was confirmed by synthesis. 相似文献
19.
Lu Yin Wenjun Shan Xingshu Li Albert S.C. Chan 《Journal of organometallic chemistry》2009,694(13):2092-111
The preparation of methyl (R)-o-chloromandelate via Ru-catalyzed asymmetric hydrogenation and transfer hydrogenation was investigated. With Ru-(R,R)-2,4,6-triisopropyl C6H2SO2-DPEN as the catalyst and HCOOH-Et3N azeotrope as the hydrogen donor, up to 92% ee was obtained in an optional condition. The synthesis of (S)-Clopidogrel was also studied. 相似文献
20.
The (Z)-isomer of a phytotoxic nonenolide, (6S,7R,9R)-6,7-dihydroxy-9-propylnon-4-eno-9-lactone isolated from Phomopsis sp. HCCB03520 and its C-6 epimer have been synthesized through a common route starting from butyraldehyde. The synthesis involves enantioselective Maruoka allylation, Sharpless asymmetric epoxidation and intramolecular ring closing metathesis as the important steps. 相似文献