Chemical Forums

Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Mitch on May 13, 2010, 04:39:01 PM

Title: Most acidic proton of doxorubicin
Post by: Mitch on May 13, 2010, 04:39:01 PM

I can't decide which -OH group attached to the aromatic 6 membered ring it might be. Hell, the one attached to the pyranose is looking good after staring at this thing long enough.  Pic attached. It supposedly has a pK_a of 8.5

Title: Re: Most acidic proton of doxorubicin
Post by: MissPhosgene on May 13, 2010, 09:33:40 PM

I agree with you. However, it would probably be pretty darn hard to deprotonate one instead of the other.

Tough question.

Title: Re: Most acidic proton of doxorubicin
Post by: AWK on May 14, 2010, 02:51:44 AM

http://www3.interscience.wiley.com/journal/113312915/abstract?CRETRY=1&SRETRY=0

Quote

Abstract
The ground- and excited-state dissociation constants and the electronic absorption and fluorescence spectra of doxorubicin were investigated by spectrophotometry. A general method for the direct calculation of individual microscopic dissociation constants was derived using the spectrophotometric data obtained. It was concluded that the protonated amino sugar group is slightly more acidic than the phenolic group. The spectrophotometric data were analyzed, and the macro- and microconstants for the various equilibria are reported.