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1.
Jisheng LuoXiaoming Yu 《Tetrahedron letters》2011,52(19):2450-2453
Generally applicable concise approaches to 3-O-acyl-l-noviose derivatives and their 3-amino bioisosteres, represented by 5 and 6, were described. Chiral aldehyde 7 was thus prepared from dimethyl l-tartrate in five steps, and converted into 5 and 6 by employing substrate induced asymmetric aldehyde or N-sulfinyl aldimine allylation and dihydropyrane epoxidation as key steps, respectively. 相似文献
2.
The formal total synthesis of the cytotoxic 14-membered macrolides, aspergillides A and B is described. A combination of a chiron approach and an asymmetric synthesis is adopted for the synthesis of the target macrolides. The required 2,6-syn and 2,6-anti tetrahydropyrans were constructed via a tandem Sharpless asymmetric epoxidation and 6-exo cyclization on δ-hydroxy allylic alcohols, as the key steps. The requisite chiral synthon was prepared from l-ascorbic acid. 相似文献
3.
The unique selective estrogen receptor modulator, Raloxifene (1), and antitubulin agent 2 were synthesized through the key intermediate, 4-methoxybenzyl 2-bromo-4-methoxyphenyl sulfoxide (6), respectively. It was found that compared with the o-sulfanyl aryl bromides, the sulfinyl group at ortho position accelerated the Sonogashira coupling reaction of aryl bromides. Thus, compound 6 was coupled with 3,4,5-trimethoxyphenyl acetylene, followed by mercury-catalyzed cyclization reaction afford compound 2 in 79% overall yield. Raloxifene (1) was prepared from compound 6 in four steps and 33% overall yield via coupling reaction with 1-trimethylsily-2-(4-tert-butyldimethylsiloxy)phenylethyne, mercury-catalyzed cyclization reaction, alkylation and demethylation. 相似文献
4.
Frieder W. Lichtenthaler Jürgen Klotz Katsumi Nakamura 《Tetrahedron: Asymmetry》2003,14(24):3973-3986
The dimethyl esters of the 2,6-anhydro-3-deoxy-hept-2-enaric acids with
-xylo,
-lyxo,
-arabino,
-lyxo- and
-ribo-configuration were synthesized from
-galactose and
-mannose, respectively, and further characterized by their di-O-acetyl and di-O-benzoyl derivatives. Comparison of their physical data with those of Daucus carota derived products revealed (−)-daucic acid to have
-lyxo-configuration 46 rather than the previously assigned
-xylo stereochemistry 1. Dimethyl daucate 43 could be converted by acid-induced ring contraction and dehydration into naturally occurring (+)-osbeckic acid 47, thereby proving its (S)-configuration. Configurational identity in the pyranoid rings of (−)-daucic acid and KDO, together with available biosynthetic evidence on chelidonic acid 4, a leaf closing factor, suggests a joint, KDO 8-P-based pathway for their biosynthesis in plants. 相似文献
5.
Abhishek Dubey 《Tetrahedron letters》2009,50(26):3425-9290
A concise and highly efficient synthesis of l-arabino-[2R,3S,4R] and l-xylo-[2R,3S,4S]-C18-phytosphingosines has been achieved. The synthetic strategy features the Sharpless kinetic resolution and tethered aminohydroxylation as the key steps. 相似文献
6.
Alain Danquigny 《Tetrahedron》2005,61(28):6772-6781
1-O-Benzylpentitols (with d-arabino, d-lyxo, d,l-xylo and d,l-ribo configurations) and aldoses dibenzyldithioacetals (with l-arabino, d-lyxo, d-xylo, d-ribo, d-galacto, d-gluco and d-manno configurations) were directly and efficiently transformed into their cyclic bis-thionocarbonate derivatives (61-73%) by reaction with diimidazolyl thione (Im2CS) in 1,4-dioxane. These bis-electrophilic adducts react regioselectively with Na2S·9H2O or Se/NaBH4 to lead regioselectively to the corresponding thiolane and selenolane rings in good yields for a short synthesis (47-65%). 相似文献
7.
Yasuko Saito Toshiyuki Takano Keita Sakakibara Hiroshi Kamitakahara Fumiaki Nakatsubo 《Cellulose (London, England)》2012,19(6):2105-2114
2,3-Di-O-myristyl-6-O-(zinc(II) phthalocyaninyl) cellulose (5) was synthesized from cellulose (1) by five reaction steps via 6-O-(3′,4′-dicyanophenyl)-2,3-di-O-myristyl cellulose (4). The key reaction was phthalocyanine-ring formation on a cellulose backbone, that is, the reaction of compound 4 with o-phthalodinitrile in the presence of hexamethyldisilazane and zinc acetate in DMF afforded to compound 5 in 35.4 % yield. Consequently, the degree of substitution with phthalocyanine moieties of compound 5 was 0.38. The LB monolayer film of compound 5 on an indium tin oxide (ITO) electrode was found to show photocurrent generation performance at 680 nm. 相似文献
8.
Om V. Singh 《Tetrahedron letters》2004,45(39):7239-7242
Use of MsCl/Et3N was proven to provide a convenient synthetic tool for the stereochemical intercoversion of the hydroxyl group in N-acetyl 1,3-aminoalcohols. Thus, under these conditions, the alcohols 4 and 6 smoothly converted to the oxazines 5 and 7, respectively, which were hydrolyzed to generate the corresponding inverted alcohols 6 and 4 in one pot. Further elaboration of 4 and 6 led to the efficient asymmetric synthesis of N-acetyl l-xylo- and l-arabino-phytosphingosines (11 and 15), respectively, via olefin cross metathesis reactions. 相似文献
9.
This paper describes a new total synthesis for (S)-2-amino-7-methoxytetralin, (S)-7-MeO-AT, from l-aspartic acid in an overall yield of 10% over nine steps. The major loss was ascribed to a key intramolecular Friedel–Crafts cyclization step, which afforded up to 36% yield. Attempts to perform a Friedel–Crafts cyclization of an intermediate phthalimide protected amino alcohol 13 did not give the desired protected (S)-7-MeO-AT. On the other hand, two new isoindolo[1,2-a]isoquinolinone derivatives 14 and 15, were isolated in 21 and 11% yield, respectively. The yield of 15 was improved to 70%. 相似文献
10.
A comparative study of the catalytic hydrogenation of benzyloxyamine hydrochloride (2a·HCl), benzyl benzohydroxamate (2b), and benzohydroxamic acid (3b) using PdC as a catalyst has disclosed that 2a·HCl smoothly undergoes the hydrogenolytic cleavage at both the benzyl—O and NO bonds, whereas 2b almost selectively suffers benzyl—O cleavage. The use of the benzyl group for protecting a hydroxamic acid function, suggested by the hydrogenolysis study, was embodied in the synthesis of rhodotorulic acid (1) starting with the reaction of 2a with bromide 5 to give 8. The key intermediate l-9 was conveniently prepared by the selective, asymmetric deacetylation of 8 using Taka-diastase. Conversion of l-9 into amino ester l-13 through the Nα-protected amino acid (l-11) and ester l-12 and coupling of l-11 with l-13 yielded dipeptide ll-14. Removal of the tert-butoxycarbonyl group from ll-14 and cyclization of the resulting amino ester produced the penultimate benzyl hydroxamate (ll-15), which was debenzylated selectively with PdC and hydrogen to furnish 1. 相似文献
11.
A common strategy for the total syntheses of the protected l-arabino- and l-ribo-C18-phytosphingosine (8 and 9, respectively), HCl salts of ent-2-epi-jaspine B (ent-6) and 3-epi-jaspine B (7) with efficient use of both flexible building blocks 26 and 27 was achieved. The key step of this approach was [3,3]-sigmatropic rearrangement of allylic trichloroacetimidate 21 and thiocyanate 22, which were derived from the known 2,3:5,6-di-O-isopropylidene-d-mannofuranose 18 as the source of chirality. The side chain functionality was installed utilizing a Wittig reaction. 相似文献
12.
Xuequan Lu 《Tetrahedron letters》2005,46(18):3165-3168
The preparations of d-ribo- and l-lyxo-phytosphingosines (1, 2) are described. Chelation-controlled addition of tetradecylmagnesium bromide to pentylidene-protected d-threitol aldehyde 6 afforded the key intermediate tetrol 7, providing the desired l-lyxo stereochemistry of phytosphingosine. Inversion at C4 of intermediate 7 provided the d-ribo stereochemistry. 相似文献
13.
Jagadish Pabba 《Tetrahedron letters》2005,46(21):3619-3622
The d-gluco-, l-ido-, d-galacto-, and l-altro-configured glycaro-1,5-lactams 1-4 were prepared from the known tartaric anhydride 5 via the aldehyde 6. These lactams are known (1) or potential (2-4) inhibitors of β-d-glucuronidases and α-l-iduronidases. Olefination of 6 to the (E)- and (Z)-alkenes 7 or 8, followed by reagent or substrate controlled dihydroxylation, lactonization, azidation, reduction, and deprotection led in 10 steps and in overall yields of 11-20% to the title lactams. 相似文献
14.
《Tetrahedron: Asymmetry》2007,18(23):2797-2802
Enantioselective syntheses of two mesityl (2,4,6-trimethylphenyl) amino acids are described. Starting from ethyl 3-mesityl-2-propenoate both enantiomeric dihydroxy esters 5 were prepared in excellent yield and enantiomeric purity (>99% ee) by Sharpless dihydroxylation. Each diol was converted into ethyl 3-azido-2-hydroxy-3-mesitylpropanoate 3 which is the common intermediate. Compound (2S,3S)-3 was transformed into Fmoc-d-mesitylglycine d-1 and Fmoc-l-mesitylalanine l-2 through two four-step-sequences. 相似文献
15.
Farah OulaïdiEstelle Gallienne Philippe Compain Olivier R. Martin 《Tetrahedron: Asymmetry》2011,22(6):609-612
The stereoselective synthesis of 1-C-alkyl iminosugars in the d-xylo and l-arabino series as potential drugs for the treatment of lysosomal diseases has been achieved. The key step involves nucleophilic addition to pentodialdofuranose-derived imines generated using enantiopure tert-butanesulfinamide. Depending on the pentofuranose configuration and structure, the stereoselectivity of this reaction was found to be controlled either by the sugar moiety or by the stereogenic sulfur center. 相似文献
16.
Andrzej Frankowski Dariusz Deredas Didier Le Nouen Thophile Tschamber Jacques Streith 《Helvetica chimica acta》1995,78(7):1837-1842
An eight-step synthetic sequence led from the known D -xylo-pentodialdose 8 to imidazo-L -xylo-piperidinose 15 , the key steps being the build-up of imidazole compound 12 by a van Leusen methodology and the intramolecular SN2 ring closure of the O-triflated benzylidene derivative 13 . xylo-Piperidinose 15 appears in a half-chair conformation like the oxocarbonium ions which are the postulated intermediates in the glycoprocessing of the pyranose polysaccharides. This bicyclic azasugar should be a glycosidase inhibitor. 相似文献
17.
Two tetrahydrofuran-based γ-amino acids [2,4-cis and 2,4-trans] were subjected to iterative peptide-coupling procedures to afford dimeric, tetrameric and hexameric carbopeptoids in good yield. These homooligomers were prepared for secondary structural study—to ascertain the conformational preference inherent in the monomer units. The l-xylo oligomers were protected with triethylsilyl ethers to increase the range of solvents suitable for structural investigation. Initial secondary structure data indicate the presence of hydrogen-bonded conformations in the l-ribo series. 相似文献
18.
A practical approach for the synthesis of the (2S,3S,4R)-trihydroxyazepane 1d has been reported. Starting from α-d-xylo-pentodialdose, readily available from d-glucose, the sequence involves Wittig olefination and reductive amination as key steps. 相似文献
19.
Hideki Jona Jun Shibata Masanori Asai Yasuhiro Goto Sachie Arai Shigeru Nakajima Osamu Okamoto Hiroshi Kawamoto Yoshikazu Iwasawa 《Tetrahedron: Asymmetry》2009,20(21):2439-2446
An efficient and practical asymmetric synthesis of 1-tert-butyl 3-methyl (3R,4R)-4-(2-oxo-2,3-dihydro-1H-benzimidazol-1-yl)piperidine-1,3-dicarboxylate 1, a useful intermediate for the synthesis of nociceptin antagonists, has been developed. This method includes the following key steps: (1) diastereoselective reduction of a chiral enaminoester 3 having (R)-1-phenylethylamine as a chiral pool constituent with the use of a combined TFA–NaBH4 reduction system and (2) efficient isomerization from 3,4-cis-substituted piperidine 8 to 3,4-trans-substituted piperidine 1 under basic conditions. The above methods proved to be applicable for large-scale operation and hundred grams of enantiomerically pure compound 1 (>98% ee) was obtained. 相似文献
20.
The Baylis-Hillman reaction of 3-O-benzyl-α-d-xylo-pentodialdo-1,4-furanose 2 afforded a diastereomeric mixture of l-ido- and d-gluco-configurated α-methylene-β-hydroxy esters 3a and 3b, respectively, in 1:1 ratio. Conjugate addition of benzyl amine on 3a gave adduct 4a as a major product while, addition of benzyl amine to 3b gave only one diastereomer 4b. Reduction of ester functionality in 4a/4b, opening of 1,2-acetonide functionality followed by reductive amino-cyclization under hydrogenation condition afforded azocanes 1c/1d in good yield. 相似文献