Synthesis of Calystegine A<sub>3</sub> from Glucose by the Use of Ring‐Closing Metathesis

Monrad, Rune Nygaard; Pipper, Charlotte Bressen; Madsen, Robert

doi:10.1002/ejoc.200900310

Cited by 29 publications

(13 citation statements)

References 34 publications

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“…Only in the case of the di‐ O ‐tritylation of allyl lactoside 7 (entry 8), an additional amount of pyridine was added in the course of the reaction, with a beneficial effect on both mobility of the mixture and reaction yield. Collectively, results in Table indicate that with a range of substrates, solvent‐free tritylations performed at 70–100 °C are much faster than under standard solution conditions; indeed from a survey of the literature, a very few number of examples were found of saccharide O ‐tritylations lasting less than 4 hours,,, also including procedures relying, unlike the protocols herein described, on DMAP catalysis.…”

Section: Resultsmentioning

confidence: 83%

Solvent-Free One-Pot Diversified Protection of Saccharide Polyols Via Regioselective Tritylations

2017

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Regioselective installation of trityl protecting groups, widely employed in organic synthesis, was demonstrated to occur in high yields on primary positions of sugar polyols in the presence of a very limited stoichiometric amount of pyridine (ca 2 equivalents) and trityl chloride (1.1 eq) at 100 8C. Under these conditions, that can be regarded as “solvent-free” conditions because of the insolubility of the polyol substrates, reactions take remarkably shorter times than in most examples reported in the literature. In addition, the method proved applicable under air without resorting to inert atmosphere. In the second part of the paper, the scope of the present tritylation approach was significantly extended with the development of streamlined “one-pot” and fully “solvent-free” sequences allowing regioselective tritylation/alkylation (or silylation) of saccharide polyols in short times and good yields, following experimentally simple protocols

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Section: Resultsmentioning

confidence: 83%

Solvent-Free One-Pot Diversified Protection of Saccharide Polyols Via Regioselective Tritylations

2017

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“…mp 143−145. 31 NaH (3.31 g, 82.76 mmol) was added at 0 °C to a stirred solution of 10 (6.02 g, 13.79 mmol) in DMF (150 mL). After 30 min MeI (11.75 g, 82.78 mmol) was added dropwise, and after 2 h the mixture was allowed to slowly reach rt.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…The 1,6-anhydro ring has been opened under standard conditions to give compound 29, which has been directly transformed into acetal form 30 with overall yield 76% after 2 steps. The glycosylation reaction of anomeric mixture of trichloroacetimidate (31) gave methyl glycoside with an 81% yield as an anomeric mixture (α:β = 3.1:1). After several unsuccessful separations we decided to change the 4′-O levulinic ester to the Fmoc ester.…”

Section: ■ Introductionmentioning

confidence: 99%

“…HRMS (ESI-TOF) m/z: [M + Na] + calcd for C 36 H 46 O 15 Na 741.2734, found 741.2729. O-(Methyl 4-O-levulinyl-2,3-di-O-methyl-α-L-idopyranosyluronate)-(1 → 4)-6-O-acetyl-2,3-di-O-benzyl-α/β-D-glucopyranosyl Trichloroacetimidate(31). Prepared according to general procedure A. Trichloroacetonitrile (444 mg, 3.08 mmol) and DBU (10 mg, 66 μmol) were added at 0 °C under argon to a stirred solution of compound 30 (221 mg, 307 μmol) in DCM (5 mL).…”

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Application of the EF and GH Fragments to the Synthesis of Idraparinux

2017

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A novel total synthesis of fully protected idraparinux has been achieved. A short and efficient protocol for the synthesis of the EF fragment of idraparinux and its C5'-epi analogue (GH unit) has been developed. The same cellobiose unit was transformed in 14 steps into the fully protected EF and GH disaccharide fragments. The key step of this approach is an epimerization of C5 by an elimination-addition sequence leading to l-ido disaccharide (GH unit) with a total yield of 24% (36% for the EF fragment). 1,6-Anhydro ring opening gave suitable substrates for efficient synthesis of fully protected idraparinux. The fully protected antithrombotic pentasaccharide idraparinux was synthesized in 23 steps for the longest linear route, with a 1.7% overall yield from d-cellobiose and d-glucose.

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“…In the first step, the corresponding xanthates were synthesized, followed by reduction via a radical reaction. 15 4-Hydroxy compound 4 was dissolved in CS 2 and THF and treated with NaH and imidazole followed by the addition of methyl iodide to get a mixture of xanthate (2S,3S,4S)-8 (55%) and the bicyclic compound 9 (42%). 16 The diastereomeric mixture of hydroxyl compounds 5 and 6 produced xanthate (2S,3S,4R)-10 and xanthate (2S,3R,4S)-11, respectively, when treated under the same reaction conditions.…”

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confidence: 99%

An Approach for Simultaneous Synthesis of cis- and trans-3-Substituted Proline-Glutamic Acid Chimeras

et al. 2012

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Synthesis of cis-and trans-3-substituted proline-glutamic acid chimeras with suitable protection for peptide synthesis through Fmoc-strategy was accomplished in six steps from benzyl (2S)-4-oxo-1-(9-phenyl-9H-fluoren-9-yl)pyrrolidine-2-carboxylate, which had been synthesized from trans-4-hydroxyproline in three steps. This methodology involved generation of cis-and trans-3-alkylated proline moieties, and manipulation of functionality and protecting groups to obtain proline-chimera monomers in appropriate form for peptide synthesis.Key words: benzyl 4-oxo-N-(9-phenylfluoren-9-yl)proline ester, alkylation, cis-and trans-3-substituted proline-glutamic acid chimeras, Fmoc-amino acid, peptides Proline plays a significant role in protein folding and refolding due to its distinctive feature of introducing a reversal in backbone conformation, which results in the nucleation of turns and breaking of helix structures in proteins. 1 When placed as a second residue (i+1) of a short and linear peptide, L-proline has been found to induce type I/II β-turns involving an intramolecular hydrogen bond between C=O of the first (i) and NH of the fourth (i+3) residue. 2 Proline chimeras, which merge side chain functionality of an amino acid with the conformational rigidity of proline, have been developed into important tools for studying the biological activity of natural amino acids and peptides. 3 3-Substituted proline moieties 4 with an appropriate side chain were found to mimic and stabilize natural β-turn types I, II, and II′. These moieties have shown high potential for the investigation of biologically active conformations of peptides and for their pharmaceutical use. 3a,e,4a,5 In past decades, several analogues of proline chimeras with different stereochemistry and functionality at C-3 position have been designed and synthesized. 3a,c,d,5b,6 Most of these methodologies were designed with the aim to synthesize a diastereomer with preferred stereochemistry, although some of them were found suitable for the synthesis of both diastereomers at the C-3 stereocenter of the proline moiety. We developed a strategy for the synthesis of both cis-and trans-3-substituted proline-glutamic acid chimeras (Figure 1) in one reaction step and in a 4:3 ratio by alkylation at the C-3 position of amino ketone 2. As both of these diastereomers were obtained in nearly equal amounts, this synthetic strategy enabled us to avoid the controlled epimerization step, which has been used widely to get a preferred enantiomer or diastereomer from a mixture of enantiomers or diastereomers, respectively. Next, necessary reaction steps were followed to obtain these diastereomers in the protected form for their incorporation into peptides. Figure 1 Stereochemical orientation of cis-and trans-3-alkylated proline moietiestrans-4-Hydroxy-L-proline (1) has emerged as a useful and versatile chiral tool for the incorporation of different functionalities into the proline moiety. A number of derivatives of this compound have been synthesized in their fully protected for...

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Synthesis of Calystegine A₃ from Glucose by the Use of Ring‐Closing Metathesis

Cited by 29 publications

References 34 publications

Solvent-Free One-Pot Diversified Protection of Saccharide Polyols Via Regioselective Tritylations

Solvent-Free One-Pot Diversified Protection of Saccharide Polyols Via Regioselective Tritylations

Application of the EF and GH Fragments to the Synthesis of Idraparinux

An Approach for Simultaneous Synthesis of cis- and trans-3-Substituted Proline-Glutamic Acid Chimeras

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Synthesis of Calystegine A3 from Glucose by the Use of Ring‐Closing Metathesis

Cited by 29 publications

References 34 publications

Solvent-Free One-Pot Diversified Protection of Saccharide Polyols Via Regioselective Tritylations

Solvent-Free One-Pot Diversified Protection of Saccharide Polyols Via Regioselective Tritylations

Application of the EF and GH Fragments to the Synthesis of Idraparinux

An Approach for Simultaneous Synthesis of cis- and trans-3-Substituted Proline-Glutamic Acid Chimeras

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Synthesis of Calystegine A₃ from Glucose by the Use of Ring‐Closing Metathesis