scholarly journals Minimizing HCN in DIC/Oxyma Mediated Amide Bond Forming Reactions

2020 ◽  
Author(s):  
Marion Erny ◽  
Marika Lundqvist ◽  
Jon H. Rasmussen ◽  
Olivier Ludemann-Hombouger ◽  
Frédéric Bihel ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Peptide Synthesis ◽  
Hydrogen Cyanide ◽  
Reaction Rate ◽  
Solid Support ◽  
Amide Bond ◽  
Prussic Acid ◽  
Bond Forming ◽  
H Nmr ◽  
Bond Forming Reactions

<p>Aiming at advancing protocols for safer, environmentally sensible peptide synthesis we report our findings with regards to the occurrence of hydrogen cyanide (HCN, prussic acid) in amide bond forming reactions mediated by diisopropylcarbodiimide (DIC) and ethyl (hydroxyimino)cyanoacetate (Oxyma). We have determined that HCN is always formed in amide bond forming reactions on solid support in N,N-dimethylformamide (DMF) when employing DIC/Oxyma. In an attempt to minimize the formation of prussic acid by means of preventing the linear DIC/Oxyma adduct <b>2</b> from cyclizing to oxadiazole <b>3</b> and in turn releasing HCN, we evaluated a series of greener solvents such as N-butylpyrrolidinone (NBP), NBP/ethyl acetate (EtOAc, 1:1), methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (PolarClean, PC), and PC/EtOAc (1:1). We found that the ratio between <b>2</b> and <b>3</b> greatly depends on the solvent used and consequently, we further examined DMF, NBP, NBP/EtOAc (1:1) and NBP/EtOAc (1:4) as solvents for DIC/Oxyma mediated amidations on solid support and in solution. We found that using carboxylic acid/Oxyma/DIC in a 1:1:1 ratio the rate of HCN formation decreases in the following order DMF>NBP>NBP/EtOAc (1:1)>NBP/EtOAc (1:4) while the reaction rate increases in order of DMF~NBPin situ scavenging of the HCN formed. We carried out DIC/Oxyma mediated amidation of Fmoc-Gly-OH + (S)-(-)-1-phenylethylamine in DMF-d<sub>7</sub> with 0, 5 and 10 equiv of dimethyl trisulfide (DMTS) as HCN scavenger. The formation of HCN and rate of amidation was monitored by <sup>1</sup>H NMR, revealing that DMTS scavenges HCN without inhibiting the rate of amidation. DIC/Oxyma mediated amidations of Fmoc‑Ser(<i>t</i>‑Bu)‑OH with (S)-(‑)-1-phenylethylamine in DMF and NBP/EtOAc (1:4) with and without 10 equiv of DMTS were carried out and found to be comparable.</p>

scholarly journals Minimizing HCN in DIC/Oxyma Mediated Amide Bond Forming Reactions

2020 ◽  
Author(s):  
Marion Erny ◽  
Marika Lundqvist ◽  
Jon H. Rasmussen ◽  
Olivier Ludemann-Hombouger ◽  
Frédéric Bihel ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Peptide Synthesis ◽  
Hydrogen Cyanide ◽  
Reaction Rate ◽  
Solid Support ◽  
Amide Bond ◽  
Prussic Acid ◽  
Bond Forming ◽  
H Nmr ◽  
Bond Forming Reactions

<p>Aiming at advancing protocols for safer, environmentally sensible peptide synthesis we report our findings with regards to the occurrence of hydrogen cyanide (HCN, prussic acid) in amide bond forming reactions mediated by diisopropylcarbodiimide (DIC) and ethyl (hydroxyimino)cyanoacetate (Oxyma). We have determined that HCN is always formed in amide bond forming reactions on solid support in N,N-dimethylformamide (DMF) when employing DIC/Oxyma. In an attempt to minimize the formation of prussic acid by means of preventing the linear DIC/Oxyma adduct <b>2</b> from cyclizing to oxadiazole <b>3</b> and in turn releasing HCN, we evaluated a series of greener solvents such as N-butylpyrrolidinone (NBP), NBP/ethyl acetate (EtOAc, 1:1), methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate (PolarClean, PC), and PC/EtOAc (1:1). We found that the ratio between <b>2</b> and <b>3</b> greatly depends on the solvent used and consequently, we further examined DMF, NBP, NBP/EtOAc (1:1) and NBP/EtOAc (1:4) as solvents for DIC/Oxyma mediated amidations on solid support and in solution. We found that using carboxylic acid/Oxyma/DIC in a 1:1:1 ratio the rate of HCN formation decreases in the following order DMF>NBP>NBP/EtOAc (1:1)>NBP/EtOAc (1:4) while the reaction rate increases in order of DMF~NBPin situ scavenging of the HCN formed. We carried out DIC/Oxyma mediated amidation of Fmoc-Gly-OH + (S)-(-)-1-phenylethylamine in DMF-d<sub>7</sub> with 0, 5 and 10 equiv of dimethyl trisulfide (DMTS) as HCN scavenger. The formation of HCN and rate of amidation was monitored by <sup>1</sup>H NMR, revealing that DMTS scavenges HCN without inhibiting the rate of amidation. DIC/Oxyma mediated amidations of Fmoc‑Ser(<i>t</i>‑Bu)‑OH with (S)-(‑)-1-phenylethylamine in DMF and NBP/EtOAc (1:4) with and without 10 equiv of DMTS were carried out and found to be comparable.</p>

scholarly journals Minimizing HCN in DIC/Oxyma-Mediated Amide Bond-Forming Reactions

2020 ◽  
Vol 24 (7) ◽  
pp. 1341-1349 ◽  
Author(s):  
Marion Erny ◽  
Marika Lundqvist ◽  
Jon H. Rasmussen ◽  
Olivier Ludemann-Hombourger ◽  
Frédéric Bihel ◽  
...  
Keyword(s):  
Amide Bond ◽  
Bond Forming ◽  
Bond Forming Reactions

Are Aminomethyl Thioesters Viable Intermediates in Native Chemical Ligation Type Amide Bond Forming Reactions?

2018 ◽  
Vol 71 (9) ◽  
pp. 697
Author(s):  
Carlie L. Charron ◽  
Jade M. Cottam Jones ◽  
Craig A. Hutton
Keyword(s):  
Amide Bond ◽  
Native Chemical Ligation ◽  
Direct Reaction ◽  
Chemical Ligation ◽  
Bond Forming ◽  
Type Process ◽  
Bond Forming Reactions ◽  
Subsequent Conversion ◽  
Three Component Coupling

The condensation of N-mercaptomethyl amines and thioesters is a potential route to amides, via aminomethyl thioester intermediates, in a native chemical ligation type process followed by self-cleavage of the ‘mercaptomethyl’ auxiliary. This paper describes investigations towards the preparation of aminomethyl thioesters, and subsequent conversion into amides, from a three-component coupling of formaldehyde, a thioacid, and an amine. Our studies suggest that while such intermediates may be formed en route to amides, no advantages are offered over the direct reaction of the amine and thioacid precursors.

Decarbonylative Sonogashira Cross-Coupling: Fruitful Marriage of Alkynes with Carboxylic Acid Electrophiles

2021 ◽  
Author(s):  
Chengwei Liu ◽  
Michal Szostak
Keyword(s):  
Carboxylic Acid ◽  
Cross Coupling ◽  
Widespread Application ◽  
Bond Forming ◽  
Strategic Value ◽  
Bond Forming Reactions

The Sonogashira cross-coupling is one of the most fundamental C–C bond forming reactions, wherein the strategic value of the alkyne moiety has found widespread application at the frontiers of organic...

scholarly journals Synthesis of amphiphilic meso-tetrasubstituted porphyrin-L-amino acid and -heterocyclic conjugates based on m-THPP

2018 ◽  
Vol 22 (11) ◽  
pp. 997-1009 ◽  
Author(s):  
Ayman M. K. Sweed ◽  
Mathias O. Senge ◽  
Sanaa M. Sh. Atta ◽  
Dalia S. Farrag ◽  
Abdel-Rahman H. Abdel-Rahman ◽  
...  
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Carboxylic Acid ◽  
Amide Bond ◽  
H Nmr ◽  
Ethylcarbodiimide Hydrochloride ◽  
Covalently Linked ◽  
Indole 3 Acetic Acid ◽  
Oxyacetic Acid ◽  
C Nmr

Two series of amphiphilic meso-tetrasubstituted porphyrin conjugates based on 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin ([Formula: see text]-THPP) covalently linked to L-amino acids and heterocycles were synthesized efficiently in the context of a program targeting new photosensitizers for PDT. 5,10,15-Tris(3-hydroxyphenyl)-20-(3-oxyacetic acid)phenyl]porphyrin and the respective trihexyl ether derivatives were conjugated with polar and non-polar natural L-amino acids such as glycine, L-proline, and L-tyrosine via an amide bond linker using [Formula: see text]-tetramethyl-[Formula: see text]-(1H-benzotriazol-1-yl)uroniumhexafluorophosphate in diisopropylethylamine (HBTU/DIPEA). [Formula: see text]-THPP was also conjugated with heterocyclic systems such as indole 3-acetic acid, 4-methylthiazole-5-carboxylic acid, and thiophene-2-carboxylic acid via ester linker using [Formula: see text]-(3-dimethylaminopropyl)-[Formula: see text]-ethylcarbodiimide hydrochloride in [Formula: see text]-hydroxysuccinamide or 1-hydroxybenzotriazole (EDCI, NHS or HOBt). The members of the two series were obtained in good yields and characterized by UV-vis, HRMS MALDI-TOF, 1H NMR and 13C NMR spectroscopy.

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