1.Sulfonate esters of 1-hydroxypyridin-2(1H)-one and ethyl 2-cyano-2-(hydroxyimino)acetate (oxyma) as effective peptide coupling reagents to replace 1-hydroxybenzotriazole and 1-hydroxy-7-azabenzotriazole
Chem Pharm Bull (Tokyo). 2010 Apr;58(4):501-6. doi: 10.1248/cpb.58.501.
A new family of sulfonate ester-type coupling reagents is described which differs in its leaving group. The sulfonate ester coupling reagents ethyl 2-cyano-2-(naphthalen-2-ylsulfonyloxyimino)acetate (NpsOXY), and ethyl 2-cyano-2-(tosyloxyimino)acetate (TsOXY) are more efficient alternatives to the benzotriazole sulfonate esters in terms of racemization suppression and coupling effectiveness. Both oxyma and its related sulfonate esters can be handled with a considerably lower risk than the explosive benzotriazole and its derivatives. 2-Oxopyridin-1(2H)-yl naphthalene-2-sulfonate (NpsOPy) and 2-oxopyridin-1(2H)-yl 4-methylbenzenesulfonate (TsOPy) sulfonate esters derived from 1-hydroxypyridin-2(1H)-one were also successfully used as new coupling reagents requiring a longer preactivation time during the coupling process. An improvement in yield and almost comparable optical purity to that of the 1-hydroxy-benzotriazole (HOBt) and 1-hydroxy-7-azabenzotriazole (HOAt) analogues was observed.
2.Reactions of monoaryl-substituted methylenecyclobutanes and methylenecyclopropanes with 1-hydroxybenzotriazole (HOBt), 1-hydroxy-7-azabenzotriazole (HOAt), and 1-hydroxysuccinimide (HOSu)
J Org Chem. 2009 Mar 20;74(6):2516-20. doi: 10.1021/jo9000299.
Monoaryl-substituted methylenecyclobutanes (MCBs) and methylenecyclopropanes (MCPs) react with 1-hydroxybenzotriazole (HOBt), 1-hydroxy-7-azabenzotriazole (HOAt), and 1-hydroxysuccinimide (HOSu) smoothly to produce the corresponding cyclobutylmethanone and cyclopropylmethanone derivatives 2, 4, and 5 via a cascade epoxidation and nucleophilic addition process or the corresponding epoxides 6 in moderate to good yields under mild conditions. A plausible mechanism has been proposed on the basis of the control experiments and the isolation of the reaction intermediates.
3.The 5,6- and 4,5-benzo derivatives of 1-hydroxy-7-azabenzotriazole
Org Lett. 2001 Sep 6;3(18):2793-5. doi: 10.1021/ol016063j.
[structure: see text]. Syntheses of the two benzo derivatives of HOAt are described. Conversion of the two isomers to the corresponding onium-style coupling reagents gave in one case a guandinium species 14 and in the other, presumably as a result of steric factors, a uronium species 15. The two systems are compared as to their effectiveness in peptide coupling processes.
