Nucleophilic replacement reactions of sulphonates

Hill, Stephen V.; Hough, L.; Richardson, Anthony C.

doi:10.1016/s0008-6215(00)81686-9

Cited by 38 publications

(13 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Protegeu-se a hidroxila de C-6 na forma de éter tert-butildimetilsilílico 23 e, em seguida, promoveu-se a mesilação da hidroxila de C-4 34 . O intermediário mesilado 38 foi submetido à reação com azida de sódio, utilizando-se DMF como solvente.…”

Section: Resultsunclassified

“…O re-síduo foi submetido à cromatografia em coluna de sílica e o produto foi eluído em hexano/acetato de etila 6,5:3,5. 34 A uma solução de 37 (1,30g, 2,7 mmol) em piridina anidra (13 mL) adicionou-se 0,7 mL (1,03 g, 9,0 mmol) de cloreto de mesila. Manteve-se a mistura de reação sob agitação magnética, em um balão fechado com um tubo de cloreto de cálcio durante 24 h. Adicionou-se solução de ácido clorídrico 2 mol/L até pH 1, extraiu-se com três porções de 30 mL de diclorometano, lavou-se a fase orgânica com 10 mL de água e secou-se a solução orgânica com sulfato de sódio anidro.…”

unclassified

See 1 more Smart Citation

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Dias¹,

Prado²,

Pinto³

et al. 2006

Quím. Nova

View full text Add to dashboard Cite

Section: Resultsunclassified

unclassified

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Dias¹,

Prado²,

Pinto³

et al. 2006

Quím. Nova

View full text Add to dashboard Cite

“…Regioselective tosylation of 5 on the primary alcohol with tosylimidazolide, MeOTf, and N-methylimidazole in THF at 0 °C afforded 6 in excellent yield. 7 Benzoylation of 6 (→ 7), followed by acid-catalyzed furan ring reconstruction in ethanol under reflux conditions, afforded the key intermediate, 2,5-anhydro-3-O-benzoylxylose diethylacetal (8), in 81% yield over three steps. The structure of 8 was confirmed by FABMS [m/z 311 (M + H) + ] and its 1 H-1 H COSY spectrum (chemical shift of H-1 moved upfield from 5.85 to 4.76 ppm).…”

mentioning

confidence: 99%

“…A literature survey suggested that the 3,4-acyloxonium ion might be formed in our experiments leading to an inseparable mixture of 3R-, 4R-, and 4S-azido-displaced products. 8 A high yield of C-4 azido-displacement can be accomplished by protecting the hydroxyl group at C-3 through alkylation (Scheme 3) as in 11, instead of through acylation (Scheme 2) as in 9. The xylose derivative 6 was benzylated with benzyl trichloroacetimidate in the presence of TMSOTf (→ 11).…”

mentioning

confidence: 99%

Stereoselective Synthesis of Cytotoxic Anhydrophytosphingosine Pachastrissamine (Jaspine B) from D‐Xylose.

Linhardt

2006

ChemInform

View full text Add to dashboard Cite

The first naturally occurring anhydrophytosphingosine, pachastrissamine (jaspine B), a marine compound cytotoxic toward P388, A549, HT29, and MEL28 cell lines at IC 50 ) 0.01 µg/mL level, has been stereoselectively synthesized from D-xylose in 10 linear steps with 25.7% overall yield.Pachastrissamine (1, Figure 1) is a natural occurring anhydrophytosphingosine derivative, first isolated in 2002 by Higa and co-workers 1 from the Okinawa marine sponge Pachastrissa sp. (family Calthropellidae). Bioassay-guided separation of the sponge crude oil led to pure 1, which exhibited a significant cytotoxicity of 0.01 µg/mL against P388, A549, HT29, and MEL28 cell lines. Almost at the same time, Debitus and coworkers 2 investigated the cytotoxicity of ethanolic extract (IC 95 ) 10 µg/mL, KB cell line) from a new species of Jaspis, a marine sponge collected in Vanuatu, and the bioguided fractionation of this extract using a brine shrimp bioassay led to two cytotoxic compounds, named as jaspine A (2, Figure 1) and jaspine B (1, Figure 1). Jaspine B hydrochloride displayed remarkable bioactivity (IC 50 ) 0.24 µM) against the A549 human lung carcinoma cell line using the ATPlite assay and represented the most potent anticancer agent on this cell line yet isolated from the Jaspis genus. High-resolution NMR, mass spectral analysis, and chemical derivatization studies suggested that the structure of pachastrissamine and jaspine B were identical, i.e., an all-syn trisubstituted tetrahedrofuran framework and the (2S,3S,4S) absolute configuration.It has been reported that sphingosine 1-phosphate induces a rapid and relevant release of arachidonic acid and increases phospholipase D activity in A549 cells. 3 To improve our understanding of this anhydrosphingosine targeting to tumor cells and explore more potent analogues based on this novel structure, we launched a stereoselective total synthesis of natural pachastrissamine (jaspine B). During our efforts, two synthetic communications 4,5 aimed to the total synthesis of pachastrissamine (jaspine B) using L-serine as starting material were published. In Rao's work, 4 a diastereoisomeric mixture of 1 was formed, using a standard asymmetric synthesis, in 10 steps and 15.4% overall yield. In Datta's letter, 5 enantiopure 1 was prepared through a bicyclic lactone intermediate in 14 steps and 15.5% overall yield from L-serine. Here, we report the stereoselective total synthesis of pachastrissamine (jaspine B).Pachastrissamine 1 can be retrosynthetically disconnected into a formylfuran derivative 3 and a commercially available alkyl Wittig reagent. The furan structure of 3 can be derived from 2,5-ring closure of an acyclic intermediate 4, which can be easily prepared from natural D-xylose through suitable functional group transformations (Scheme 1).D-Xylose treated with concentrated H 2 SO 4 in acetone 6 gave 1,2-acetal 5 in 82% yield (Scheme 2). Regioselective tosylation of 5 on the primary alcohol with tosylimidazolide, MeOTf, and N-methylimidazole in THF at 0°C afforded 6 in excellent y...

show abstract

“…Except for the 6-sulfonate of galactopyranoside derivatives, direct nucleophilic displacement of the sulfonyloxy group attached to the primary (C-6) carbon atom is considerably faster than direct nucleophilic displacement of sulfonates attached to a secondary carbon atom of the pyranoid ring, permitting thus the selective displacement of the former. 4,7 In the absence of a d-trans-axial substituent, the C-4 sulfonyloxy group of a /3-D-hexopyranoside is much more reactive toward the direct nucleophilic displacement than the C-2 sulfonate. Thus, whereas the direct nucleophilic displacement with benzoate of an equatorially oriented C-4 sulfonyloxy group in refluxing N,Ndimethylformamide is complete in 16 hr (D-galacto isomer reacts ca.…”

mentioning

confidence: 99%

Neighboring-group participation in carbohydrate chemistry. V. Direct evidence for the participation of the .beta.-trans-axial benzoyloxy group in the nucleophilic displacement of methylsulfonates of pyranoside

Miljković¹,

Glisin²,

Gligorijevic³

1975

J. Org. Chem.

View full text Add to dashboard Cite

Refluxing of an N,N-dimethylformamide solution of methyl 4,6-di-0benzoyl-3-0-methyl-2-0-methylsulfonyl-8-D-galactopyranoside (7) (120 hr) or methyl 2,6-di-Obenzoyl-3-0-methyl-4-O-methylsulfonyl-~-~-mannopyranoside (11) (10 hr) with potassium benzoate gave methyl 2,4,6-tri-0-benzoyl-3-~-methyl-~-D-galactopyranoside (4) and methyl 2,4,6-tri-0-benzoyl-3-~-methyl-~-D-mannopyranoside (6) as the only isolable products, the 6:4 ratio being the same in both cases (-3:l). The greater reactivity of 11 vs. 7, as well as the predominant formation of 6 vs. 4 was rationalized in terms of the electron-withdrawing effect of the anomeric carbon atom.

show abstract

Nucleophilic replacement reactions of sulphonates

Cited by 38 publications

References 28 publications

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Síntese de aliloxi-orto-iodobenzamida derivada de d-glicose e reação de ciclização radicalar mediada por hidreto de tri-n-butilestanho

Stereoselective Synthesis of Cytotoxic Anhydrophytosphingosine Pachastrissamine (Jaspine B) from D‐Xylose.

Neighboring-group participation in carbohydrate chemistry. V. Direct evidence for the participation of the .beta.-trans-axial benzoyloxy group in the nucleophilic displacement of methylsulfonates of pyranoside

Contact Info

Product

Resources

About