Thiopeptide Synthesis. α-Amino Thionoacid Derivatives of Nitrobenzotriazole as Thioacylating Agents

Ma, Shenglin; Cw, Grote; Rapoport, Henry

doi:10.1021/jo961245q

Cited by 129 publications

(111 citation statements)

References 19 publications

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“…In general the thionation of amides is the most useful method for replacing the oxygen of amides by sulfur. In this sense, several methods have been reported through direct treatment of the amide with thionating reagents such as P 4 S 10 [6], Lawesson's reagent [7], R 3 OBF 4 /NaSH [8], P 4 S 10 /Na 2 CO 3 [9], P 4 S 10 /Al 2 O 3 [10]; or by prior activation of the amide with an electrophilic reagent, for example, a combination of oxalyl chloride or phosphorus oxychloride with benzyltriethylammonium tetrathiomolybdate [11], phosphorus oxychloride with hexamethyldisilathiane [12], and triflic anhydride with aqueous ammonium sulfide [13].…”

Section: Introductionmentioning

confidence: 99%

An expedient approach to ferrocenyl thioamides via Fischer carbenes

Sandoval-Chávez

López‐Cortés

Gutiérrez-Hernández

et al. 2009

Journal of Organometallic Chemistry

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Section: Introductionmentioning

confidence: 99%

An expedient approach to ferrocenyl thioamides via Fischer carbenes

Sandoval-Chávez

López‐Cortés

Gutiérrez-Hernández

et al. 2009

Journal of Organometallic Chemistry

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“…There has been a surge in the synthesis of thio analogues of peptides and related intermediates, the replacement of O with S yielding novel unnatural amino acids and peptidomimetics such as thiopeptides, 36 thioureas, and isothiocyanates 37 possessing therapeutic importance. Sulfur-containing compounds such as thioamides and thioesters have been found to be better reactants in the preparation of several heterocycle-tethered peptidomimetics and other related compounds compared to their oxygenated analogues.…”

Section: Methodsmentioning

confidence: 99%

Cyanogen Bromide as Dehydrosulfurizing Agent for the Synthesis of Nβ-Fmoc-Amino Alkyl Isonitriles from Nβ-Fmoc-Amino Alkyl Thioformamides

Vishwanatha¹,

Hemantha²,

Sureshbabu³

2010

Synlett

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Synthetically useful N b -Fmoc amino alkyl isonitriles are prepared conveniently from N b -Fmoc amino alkyl thioformamides via a cyanogen bromide mediated dehydrosulfurization. The reaction is fast, clean, and yields are good.Key words: N b -Fmoc-amino alkyl thioformamides, isonitriles, dehydrosulfurization, cyanogen bromideIn recent years, the synthetic utility of isonitriles 1 in organic reactions has been exploited. Compounds containing an isocyano group find use as antibiotics, 2 antineoplastics, 3 and antianaesthetics. 4 The synthetic utility of isonitriles arises from their divergent character 5 and this functionality has wide utility, such as in the preparation of isothiocyanates, 6 N,N-dialkylcarbodiimides, 7 1-substituted tetrazoles, 8 [16][17][18][19][20] has been well demonstrated.In peptide chemistry, the application of isonitrile derivatives of amino acids has led to a variety of peptidomimetics 21 and other useful products such as blactams, 22 glycopeptides, 23 depsipeptides, 24 peptide nucleic acids, 25 and N-hydroxy peptides. 26 Amino acid ester derived isonitriles are the known entities, which are prepared from corresponding formyl amino acid esters. 27A recent entry into this new class of amino acid derived isonitriles has been described by our group wherein N bFmoc amino alkyl isonitriles were obtained through carboxyl group modification. 28Of the many methods available for the preparation of isonitriles, dehydration of formamides is the widely followed route in amino acid chemistry, showing general applicability and reproducibility. 29 Reaction of alkyl halides with heavy metal cyanide salts, 30 addition of dichlorocarbene to amines, 31 reduction of isocyanates and isothiocyanates 32 are other available routes. Dehydration of formamides has been carried out by using tosyl chloride, phosphorus oxychloride (POCl 3 ) in the presence of a base, cyanuric chloride, triphenyl phosphine-CCl 4 , phosgene, diphosgene, and triphosgene. 33 The method employing POCl 3 being quite harsh is found to cause racemization and therefore is not applicable in peptide chemistry, and isolation of enantiomerically pure isonitriles is always challenging and demanding. Danishefsky and co-workers have isolated enantiomerically pure aisocyanoesters 34 derived from formyl amino acid esters, employing triphosgene/N-methylmorpholine (NMM) at -78°C. Nenajdenko's group has synthesized the amino acid derived nonracemic isonitriles employing the less commonly used 4-methyl-2,6,7-trioxabicyclo[2.2.2] octyl-protected formyl amino ester.35 Sureshbabu et al. reported the synthesis and isolation of enantiomerically pure N-Fmoc-amino alkyl isonitriles by the dehydration of the corresponding N b -Fmoc amino alkyl formamides under neutral conditions employing Burgess' reagent.28 In a continuation of our current studies on isonitriles, we sought a simple and economically viable route involving dehydrosulfurization of N b -Fmoc amino alkyl thioformamides using cyanogen bromide (CNBr, Scheme 1). Scheme 1There has been a sur...

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“…N-acylureas are mild acylating agents that have previously been explored in peptide synthesis by Pascal et al [13,14] and for thioamide synthesis by Rapoport et al [15] and Zacharie et al [16] However, the utility of these groups as acylating agents has been limited due to the low reactivity of N-acylurea products towards aminolysis and the base lability of previous Nacylurea forming linkers. [13] Inspired by this work, we have found that o-aminoanilides 1 are stable synthetic intermediates that can be efficiently transformed into an aromatic N-acylurea moiety 2 [14,16] following chain elongation (Scheme 1).…”

Section: Juan B Blanco-canosa and Philip E Dawson*mentioning

confidence: 99%