Editing Guanidinylation (section)

== HBTU  ==

2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate&nbsp;<span style="line-height: 1.5em;">[http://www.sigmaaldrich.com/catalog/product/aldrich/12804?lang=en&region=US Sigma 12804-1G-F $31.90]</span> 

<span style="line-height: 1.5em;">Recent studies show that crystal as well as solution structure of this coupling agent is a guanidinium N-oxide and not an uronium compound;1 Coupling reagent for peptide synthesis; advantages are: very low racemization, simple reaction conditions, very short reaction time, and high yields</span> 

In a solution of bPEI&nbsp;(30mg, dissolved in 5mL dry DMF) and TEA (6.07 𝜇L,&nbsp;2.5 equivalents), HBTU (6.62mg, 0.17mmol for 10% substitution)&nbsp;was added and the reaction mixture was stirred&nbsp;for 12 h at ambient temperature. Then the reaction mixture<br>was poured in a dialysis bag (12 kDa cut-off) and dialyzed&nbsp;against 1M HCl solution for 24 h followed by against 1M&nbsp;NaCl (pH 8.5) solution for 24 h and deionized water for&nbsp;48 h with intermittent change of respective solutions/water.&nbsp;Subsequently, the dialyzed solution was lyophilized to obtain&nbsp;TP1 as white solid in ∼78% yield. Similarly, other modified&nbsp;polymers, namely, TP2, TP3, TP4, and TP5, were prepared&nbsp;by varying the amounts of HBTU in 75–83% yield. These&nbsp;modified polymers were then characterized by 1H-NMR.&nbsp;TP5: 1H-NMR (D2O) 𝛿 (ppm): 2.4–2.65 (m, −NCH2&nbsp;−, PEI)&nbsp;2.75 (br s, −NCH3, TMG). 

[[Image:PEI gu HBTU reaction.jpg|650px|PEI gu HBTU reaction.jpg]] 

[[Image:PEI gu HBTU.jpg|650px|PEI gu HBTU.jpg]] 

[[Category:Transfection]] [[Category:Paul]]