Desulfurization with nickel and cobalt boride: scope, selectivity, stereochemistry, and deuterium-labeling studies

Back, Thomas G.; Baron, D. L.; Yang, Kexin

doi:10.1021/jo00061a011

Cited by 115 publications

(86 citation statements)

References 5 publications

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“…Better results were obtained by treating the cycloadduct with NiCl 2 ± NaBH 4 in a methanol/tetrahydrofuran solvent mixture [20] at À 10 8C for 10 min. The 2-deoxy glycoside 42 was prepared in 45 % yield under these milder conditions.…”

Section: Synthesis Of Aryl 2-deoxy-o-glycosidesmentioning

confidence: 99%

ortho-Thioquinones, New Acceptors for the Stereoselective Synthesis of Aryl 2-Deoxy-O-Glycosides

et al. 1999

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Abstract:a-Hydroxynaphthylthiophthalimide (1) is a suitable precursor of the reactive ortho-thioquinone 2, which can be generated in situ and trapped by glycals. The reaction is an inverse electron-demand [42] cycloaddition that occurs in a totally regioselective and highly stereoselective way. A series of differently substituted glycals (3, 5 ± 12, 21, 22, 38) as well as various ortho-thioquinones (25 ± 27) are successfully used as electron-rich dienophiles and electron-poor dienes, respectively, with chloroform, dimethylformamide, and dimethyl sulfoxide as solvents. The stereochemistry of substituents on the dienophile strongly influences the selectivity of the cycloaddition, which becomes totally stereoselective when galactals 8 ± 10 or arabinals 21 and 22 are employed as dienophiles. Among the heterodienes tested, the a-naphthol derivative 25 and the tyrosine derivative 26 were successfully used to prepare the naphthyl-a-O-rhamnoside 32 a and the tyrosine-a-O-glucoside 34, respectively. Cycloadducts 4 a, 17, 24, and 33 a were successfully desulfurized, affording the corresponding aryl 2-deoxy-a-O-glycosides 39 and 40 ± 42.

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Section: Synthesis Of Aryl 2-deoxy-o-glycosidesmentioning

confidence: 99%

ortho-Thioquinones, New Acceptors for the Stereoselective Synthesis of Aryl 2-Deoxy-O-Glycosides

et al. 1999

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“…7 Progress of desulfurisation was monitored by LC-ESI-MS and the reaction was completed within 24 hours. Fig.…”

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confidence: 99%

Identification of the amino acid labionin and its desulfurised derivative in the type-III lantibiotic LabA2 by means of GC/MS

2011

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A GC-MS method for the rapid and unambiguous identification of the amino acid labionin (Lab) occurring in type-III lantibiotics is presented. This method will constitute a valuable tool for the characterisation and structure elucidation of labyrinthopeptins and their differentiation from lanthionine-type lantibiotics.Lantibiotics are ribosomally synthesised peptide antibiotics containing the thioether amino acids (2S,6R)-meso-lanthionine (Lan, 1) and/or (2S,3S,6R)-3-methyl-lanthionine (MeLan, 2). 1 As further structural modifications lantibiotics may contain a,b-unsaturated amino acids such as 2,3-didehydroalanine (Dha, 3) and 2,3-didehydroaminobutyric acid (Dhb, 4). Lantibiotics are produced by a wide range of Gram-positive bacteria, e.g. Staphylococci and Lactococci, and mostly have antimicrobial activity against other Gram-positive bacteria.Recently, we identified a new structural type of lantibiotics, named labyrinthopeptins, which are produced by the Actinomycete Actinomadura namibiensis DSM6313. 2 The structure model of Labyrinthopeptin A2 (LabA2, 6a) showed the presence of an unusual a,a-disubstituted amino acid, named labionin (Lab, 5). From X-ray data it was deduced that Lab (5) has (2S,4S,8R)-configuration. Lab (5) can be structurally considered as a triamino triacid consisting of a basic lanthionine motif, which is further extended at the quaternary C-a-atom by a methylene bridge and an a-amino acyl residue, thus enabling the formation of two ring systems within a peptide chain. From the sequence of labyrinthopeptin prepropeptides it was deduced that a Ser/Ser/Cys motif is the precursor of Lab (5). Searches in databases containing genomic data showed that gene clusters with similar architecture and high sequence homology to the labyrinthopeptin gene cluster are widespread among Actinomycetes, e.g. Streptomyces coelicolor, S. avermitilis, and Saccharopolyspora erythraea. Based on those similarities we assume that they are producers of labyrinthopeptin-type lantibiotics. It is particularly interesting that their lantibiotic precursor peptides also contain the Ser/Ser/Cys motif, which could be a precursor of the Lab (5) motif (Fig. 1).

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“…To our delight, treatment of a solution of hemithioacetal 3a and nickel chloride hexahydrate in a mixture of methanol and tetrahydrofuran with sodium borohydride at 0 °C following the protocol reported by Back et al [28–29] provided the desired glucoside 4a in 80% yield (Scheme 1). Hemithioacetals 3a–d were transformed into their corresponding glucosides 4a–d in moderate to excellent yields (Scheme 1).…”

Section: Resultsmentioning

confidence: 99%

Synthesis of 1,2-cis-2-C-branched aryl-C-glucosides via desulfurization of carbohydrate based hemithioacetals

Kinfe¹,

Mebrahtu²,

Manana³

et al. 2015

Beilstein J. Org. Chem.

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Summary1-C and 2-C-branched carbohydrates are present as substructures in a number of biologically important compounds. Although the synthesis of such carbohydrate derivatives is extensively studied, the synthesis of 1,2-cis-2-C-branched C-, S-, and N-glycosides is less explored. In this article a synthetic strategy for the synthesis of 1,2-cis-2-C-branched-aryl-C-glucosides is reported via a hydrogenolytic desulfurization of suitably orientated carbohydrate based hemithioacetals. 1,2-cis-2-Hydroxymethyl and 2-carbaldehyde of aryl-C-glucosides have been synthesized using the current strategy in very good yields. The 2-carbaldehyde-aryl-C-glucosides have been identified as suitable substrates for the stereospecific preparation of 2,3-unsaturated-aryl-C-glycosides (Ferrier products).

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Desulfurization with nickel and cobalt boride: scope, selectivity, stereochemistry, and deuterium-labeling studies

Cited by 115 publications

References 5 publications

ortho-Thioquinones, New Acceptors for the Stereoselective Synthesis of Aryl 2-Deoxy-O-Glycosides

ortho-Thioquinones, New Acceptors for the Stereoselective Synthesis of Aryl 2-Deoxy-O-Glycosides

Identification of the amino acid labionin and its desulfurised derivative in the type-III lantibiotic LabA2 by means of GC/MS

Synthesis of 1,2-cis-2-C-branched aryl-C-glucosides via desulfurization of carbohydrate based hemithioacetals

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