18303-10-1Relevant articles and documents
DirectN-glycosylation of tosyl and nosyl carbamates with trichloroacetimidate donors
Khanam, Ariza,Mandal, Pintu Kumar
supporting information, p. 15386 - 15391 (2021/09/07)
Under catalyst and additive-free conditions, a convenient and highly efficient eco-friendly method for the stereoselective synthesis ofN-glycofuranosyl and glycofuranosyl sulfonamides has been developed. The two-component reaction of glycofuranosyl trichloroacetimidates with a wide range of tosyl and nosyl carbamate acceptors having varying pKa-values including non-sugar-, and sugar-derived carbamates as well as amino acid-derived carbamates, proceeded smoothly with good yield and β-stereoselectivity. In addition, the selective deprotection ofN-carbamates andN-sulfonyl groups of theN-glycoside functioning as orthogonal protective groups was performed for further functionalization of theN-glycosides.
Self-promoted and stereospecific formation of N-glycosides
Nielsen, Michael Martin,Ma?a, Patrycja,Baldursson, Eirikur Pórir,Pedersen, Christian Marcus
, p. 5299 - 5307 (2019/05/29)
A stereoselective and self-promoted glycosylation for the synthesis of various N-glycosides and glycosyl sulfonamides from trichloroacetimidates is presented. No additional catalysts or promoters are needed in what is essentially a two-component reaction. When α-glucosyl trichloroacetimidates are employed, the reaction resulted in the stereospecific formation of the corresponding β-N-glucosides in high yields at ambient conditions. On the other hand, when equatorial glucosyl donors were used, the stereospecificity decreased and resulted in a mixture of anomers. By NMR-studies, it was concluded that this decrease in stereospecificity was due to an, until now, unpresented anomerization of the trichloroacetimidate under the very mildly acidic conditions. The mechanism and kinetics of the glycosylations have been studied by NMR-experiments, which gave an insight into the activation of trichloroacetimidates, suggesting an SNi-like mechanism involving ion pairs. The scope of glycosyl donors and sulfonamides was found to be very broad including popular N-protective groups and common glycosyl donors of various reactivity. Peracetylated GlcNAc trichloroacetimidate could be used without the need for any promotors or additives and a tyrosine side chain was glycosylated as an N-glycosyl carbamate. The N-carbamates and the N-sulfonyl groups functioned as orthogonal protective groups of the N-glycoside and hence allowed further N-functionalization without risking mutarotation of the N-glycoside. The N-glycosylation was also performed on a gram scale, without a drop in stereoselectivity nor yield.
Rapid and straightforward transesterification of sulfonyl carbamates
Isaksson, Rebecka,Kumpi?a, Ilze,Larhed, Mats,Wannberg, Johan
supporting information, p. 1476 - 1478 (2016/03/12)
A fast and convenient method for the alkoxy exchange of sulfonyl carbamates by simply heating in a chosen alkyl alcohol is described. No catalysts or additives are required. Microwave heating at 100-120 °C for 20-60 min resulted in good to excellent yields (53-93%) of alkyl (arylsulfonyl)carbamates where the alkyl part originates from the alcohol solvent. The developed protocol was applied to the synthesis of an angiotensin II type 2 receptor (AT2R) ligand.
Microwave Promoted Transcarbamylation Reaction of Sulfonylcarbamates under Continuous-Flow Conditions
Kumpina, Ilze,Isaksson, Rebecka,S?vmarker, Jonas,Wannberg, Johan,Larhed, Mats
supporting information, p. 440 - 445 (2016/03/04)
Successful conditions for the transcarbamylation/transesterification reaction of sulfonylcarbamates with alcohols by microwave heating under continuous-flow conditions were developed. After optimization of the processes, two series of O-alkylsulfonylcarbamates were obtained in high yields and purities using microwave transparent borosilicate tube reactors. In order to also illustrate the usefulness of the protocol in a medicinal chemistry context, the methodology was used for the synthesis of three angiotensin II type 2 receptor ligands.
Sulfonyl Azides as Precursors in Ligand-Free Palladium-Catalyzed Synthesis of Sulfonyl Carbamates and Sulfonyl Ureas and Synthesis of Sulfonamides
Chow, Shiao Y.,Stevens, Marc Y.,Odell, Luke R.
, p. 2681 - 2691 (2016/04/26)
(Chemical Equation Presented). An efficient synthesis of sulfonyl carbamates and sulfonyl ureas from sulfonyl azides employing a palladium-catalyzed carbonylation protocol has been developed. Using a two-chamber system, sulfonyl azides, PdCl2, and CO gas, released ex situ from Mo(CO)6, were assembled to generate sulfonyl isocyanates in situ, and alcohols and aryl amines were exploited as nucleophiles to afford a broad range of sulfonyl carbamates and sulfonyl ureas. A protocol for the direct formation of substituted sulfonamides from sulfonyl azides and amines via nucleophilic substitution was also developed.
A catalytic, Bronsted base strategy for intermolecular allylic C-H amination
Reed, Sean A.,Mazzotti, Anthony R.,White, M. Christina
supporting information; experimental part, p. 11701 - 11706 (2009/12/08)
A Bronsted base activation mode for oxidative, Pd(II)/sulfoxide- catalyzed, intermolecular C-H allylic amination is reported. N,N-diisopropylethylamine was found to promote amination of unactivated terminal olefins, forming the corresponding linear allylic amine products with high levels of stereo-, regio-, and chemoselectivity. The predictable and high selectivity of this C-H oxidation method enables latestage incorporation of nitrogen into advanced synthetic intermediates and natural products.
Catalytic intermolecular linear allylic C-H amination via heterobimetallic catalysis
Reed, Sean A.,White, M. Christina
, p. 3316 - 3318 (2008/10/09)
A novel heterobimetallic Pd(II)sulfoxide/(salen)Cr(III)Cl-catalyzed intermolecular linear allylic C-H amination (LAA) is reported. This reaction directly converts densely functionalized α-olefin substrates (1 equiv) to linear (E)-allylic carbamates with good yields and outstanding regio- and stereoselectivities (>20:1). Chiral bis-homoallylic and homoallylic oxygen, nitrogen, and carbon substituted α-olefins undergo allylic C-H amination with good yields, excellent selectivities, and no erosion in enantiomeric purity. Streamlined routes to (E)-allylic carbamates that can be further elaborated to medicinally and biologically relevant allylic amines are also demonstrated. Valuable 15N-labeled allylic amines may be generated directly from allyl moieties at late stages of synthetic routes by using the readily available 15N-(methoxycarbonyl)-p-toluenesulfonamide nucleophile. Evidence is provided that this reaction proceeds via a heterobimetallic mechanism where Pd/sulfoxide mediates allylic C-H cleavage to form a π-allylPd intermediate, and (salen)Cr(III)Cl/BQ work together to promote functionalization with the nitrogen nucleophile. Copyright
Scavenge-ROMP-filter: a facile strategy for soluble scavenging via norbornenyl tagging of electrophilic Reagents.
Moore, Joel D,Harned, Andrew M,Henle, Julia,Flynn, Daniel L,Hanson, Paul R
, p. 1847 - 1849 (2007/10/03)
[reaction: see text] A new "chemical tagging" method for homogeneous electrophilic scavenging is described. The method utilizes 5-norbornene-2-methanol to scavenge/tag a variety of electrophiles that are present in excess. Once tagging is complete, the crude reaction mixture is subjected to a rapid ROM polymerization event utilizing the second generation Grubbs catalyst. This process yields a polymer that can be precipitated with methanol or ether/hexane, leaving products in excellent yield and purity.
Selective Cathodic Cleavage of Unsymmetrical Imidodicarbonates, Acylcarbamates and Diacylamides
Maia, Hernani L. S.,Monteiro, Luis S.,Degerbeck, Fredrik,Grehn, Leif,Ragnarsson, Ulf
, p. 495 - 500 (2007/10/02)
A study of the selective cathodic cleavage of one of the alkoxycarbonyl or acyl groups from various imidodicarbonates, acylamides, and diacylamides is reported.The compounds investigated include all 15 possible combinations of the following groups in unsymmetrical N,N-diprotected derivatives of benzylamine: p-nitrobenzyloxycarbonyl, trichloroethyloxycarbonyl, toluene-p-sulfonyl, benzoyl, benzyloxycarbonyl, and tert-butyloxycarbonyl which can all be electrochemically cleavaged, except the last one.Initially the compounds were examined by cyclic voltammetry in order to measure the potentials associated with the cleavage of each group and afterwards they were electrolysed at constant potential in the presence of a proton donor.The following ranges in negative potential were recorded: 1.03-1.13 V , 1.8-2.14 V (Troc), 1.75-2.41 V (Tos), 1.88-2.52 V (Bz), and 2.83-2.9 V (Z), thus occasionally revealing a drastic effect of the auxiliary group.In the eletrolytic experiments competitive attack by base occasionally led to mixtures of monoacylamides.However, all compounds apart from some of the trichloroethyloxycarbonyl derivatives could be selectively cleaved in 89-100percent yields when an appropriate proton donor was used.Tentative explanations are given for the behaviour of the compounds studied and some conclusions are drawn.
Direct Synthesis of N-Protected Chiral Amino Acids from Imidodicarbonates employing either Mitsunobu or Triflate Alkylation. Feasibility Study using Lactate with Particular Reference to 15N-Labelling
Degerbeck, Fredrik,Fransson, Bengt,Grehn, Leif,Ragnarsson, Ulf
, p. 245 - 254 (2007/10/02)
Two novel approaches to N,N-diprotected chiral α-amino acid esters, based on selected imidodicarbonates as amine synthons, have been explored.Thus, N-alkylation of these substrates was smoothly accomplished by the Gabriel or Mitsunobu methods as well as by the use of triflates.Ethyl (R,S)-2-bromopropionate underwent nucleophilic substitution when treated with the potassium salt of selected imidodicarbonates in dry dimethylformamide to furnish the corresponding fully blocked (R,S)-alanines in high yield. the chirality of ethyl (S)-lactate was largely conserved when it was condensed with free imidodicarbonates and tosylcarbamates under conventional Mitsunobu conditions.The yield of the corresponding N,N-di-protected ethyl (R)-alaninate was strongly dependent of the electron-withdrawing properties of the imidodicarbonate alkyl groups.Thus, Boc2NH gave 5 percent of the product whereas Troc-NH-Z afforded the corresponding analogue in 83 percent yield under comparable conditions.On the other hand, triflates of various lactic acid esters reacted smoothly with the lithium salt of Boc2NH, also with clean inversion, as a result of which, after selective removal of two blocking groups, the N-protected alanine of opposite configuration could be isolated in high yield and excellent stereochemical purity.Both methods have been used for the synthesis of 15N-labelled N-protected (R)- and (S)-alanines, suitable for direct application to peptide synthesis.
