- Photooxidation of thiosaccharides mediated by sensitizers in aerobic and environmentally friendly conditions
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A series of β-d-glucopyranosyl derivates have been synthesized and evaluated in photooxidation reactions promoted by visible light and mediated by organic dyes under aerobic conditions. Among the different photocatalysts employed, tetra-O-acetyl riboflavin afforded chemoselectively the respective sulfoxides, without over-oxidation to sulfones, in good to excellent yields and short reaction times. This new methodology for the preparation of synthetically useful glycosyl sulfoxides constitutes a catalytic, efficient, economical, and environmentally friendly oxidation process not reported so far for carbohydrates.
- Traverssi, Miqueas G.,Pe?é?ory, Alicia B.,Varela, Oscar,Colomer, Juan P.
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p. 9262 - 9273
(2021/03/16)
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- Synthesis and conformational analysis of neoglycoconjugates derived from O- and S-glucose
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Using olefin metathesis as a key step, four neoglycoconjugates incorporating α-O-glucose, α-S-glucose or β-S-glucose as a carbohydrate unit and l-serine or l-cysteine as an amino acid moiety have been synthesized. The four-atom carbon spacer allows the carbohydrate to explore a wide-ranging conformational space, which may have important implications for the molecular recognition of these molecules.
- Rojas, Víctor,Carreras, Javier,Corzana, Francisco,Avenoza, Alberto,Busto, Jesús H.,Peregrina, Jesús M.
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- Stereoselective synthesis of β-glycosyl thiols and their synthetic applications
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A significantly fast reaction condition for the exclusive preparation β-glycosyl thiol derivatives has been developed successfully. The reaction condition is one-step, fast, high yielding, highly stereoselective, and requires only benchtop chemicals. Further reaction of glycosyl thiol derivatives with Michael acceptors and alkylating agents furnished thioglycosides and (1,1)-thiolinked trehalose analogs.
- Jana, Manas,Misra, Anup Kumar
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p. 2680 - 2686
(2013/04/24)
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- DECHALCOGENATIVE METHODS FOR THE PREPARATION OF ALLYLIC SULFIDES
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A dechalcogenative method for the preparation of an allylic sulfide comprises contacting an activated chalcogenide of Formula (I) with a thiol of Formula (II) for a period of time sufficient to form an intermediate of Formula (III), and supplying sufficient activation energy to the intermediate of Formula (III), in a suitable solvent, preferably in the absence of a phosphine or other thiophile, to induce a [2,3]-sigmatropic rearrangement therein to form an allylic sulfide of Formula (IV), with concomitant loss of chalcogen Z, as set forth in the following reaction scheme, wherein X is an activating group selected from the group consisting of CN, S-pyridyl, S-heteroaryl, SO2-aryl, and SO3Y; Y is an alkali metal ion; Z is Se or S; R1, R2, R3, R4, and R5 are each independently H or a hydrocarbon moiety; and R is an organic moiety.
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Page/Page column 10
(2008/12/08)
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- Dechalcogenative allylic selenosulfide and disulfide rearrangements: Complementary methods for the formation of allylic sulfides in the absence of electrophiles. Scope, limitations, and application to the functionalization of unprotected peptides in aqueous media
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Primary allylic selenosulfates (seleno Bunte salts) and selenocyanates transfer the allylic selenide moiety to thiols giving primary allylic selenosulfides, which undergo rearrangement in the presence of PPh3 with the loss of selenium to give allylically rearranged allyl alkyl sulfides. This rearrangement may be conducted with prenyl-type selenosulfides to give isoprenyl alkyl sulfides. Alkyl secondary and tertiary allylic disulfides, formed by sulfide transfer from allylic heteroaryl disulfides to thiols, undergo desulfurative allylic rearrangement on treatment with PPh3 in methanolic acetonitrile at room temperature. With nerolidyl alkyl disulfides this rearrangement provides an electrophile-free method for the introduction of the farnesyl chain onto thiols. Both rearrangements are compatible with the full range of functionality found in the proteinogenic amino acids, and it is demonstrated that the desulfurative rearrangement functions in aqueous media, enabling the derivatization of unprotected peptides. It is also demonstrated that the allylic disulfide rearrangement can be induced in the absence of phosphine at room temperature by treatment with piperidine, or simply by refluxing in methanol. Under these latter conditions the reaction is also applicable to allyl aryl disulfides, providing allylically rearranged allyl aryl sulfides in good yields.
- Crich, David,Krishnamurthy, Venkataramanan,Brebion, Franck,Karatholuvhu, Maheswaran,Subramanian, Venkataraman,Hutton, Thomas K.
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p. 10282 - 10294
(2008/03/12)
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- Microwave irradiation for accelerating the synthesis of thioglycosides
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A simple and efficient procedure for the synthesis of thioglycosides has been achieved from the reaction of glycosylisothiouronium salts with alkyl or heteroaryl halides under microwave irradiation, in much shorter times and in yields comparable with conventional methods. Copyright Taylor & Francis Group, LLC.
- El Ashry,Awad,Hamid, H. M. Abdel,Atta
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p. 2769 - 2785
(2007/10/03)
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- Allylic selenosulfide rearrangement: A method for chemical ligation to cysteine and other thiols
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Alkylation of potassium selenosulfate with allylic halides gives Se-allyl seleno Bunte salts. On reaction with thiols at room temperature, these afford mixed dialkyl selenosulfides, which undergo 2,3-sigmatropic rearrangement with loss of selenium, either spontaneously or with assistance by triphenylphosphine, thereby providing mixed dialkyl sulfides and a new permanent chemical ligation method. The process is illustrated through the lipidation of cysteine-containing tripeptides and by the allylation of 1-thioglucose tetraacetate. Copyright
- Crich, David,Krishnamurthy, Venkataramanan,Hutton, Thomas K.
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p. 2544 - 2545
(2007/10/03)
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- Modified one-pot protocol for the preparation of thioglycosides from unprotected aldoses via S-glycosyl isothiouronium salts
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An efficient one-pot protocol for the direct preparation of thioglycosides starting from unprotected reducing sugars via S-glycosyl isothiouronium salts is reported. In this one-pot methodology, BF3·OEt2 has been used as a general catalyst for both per-O-acetylation of sugars and conversion of sugar per-O-acetates into S-glycosyl isothiouronium salts, which was allowed to react with alkylating agents in the presence of a base to furnish thioglycosides in excellent yield. Copyright Taylor & Francis, Inc.
- Tiwari, Pallavi,Agnihotri, Geetanjali,Misra, Anup Kumar
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p. 723 - 732
(2007/10/03)
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