Linear free energy relationship of the cis to trans epimerization of substituted 1-phenyl-1,2,3,4-tetrahydro-β-carbolines

ORGN 510

Michael L. Van Linn, mvanlinn@uwm.edu1, F. Holger Försterling1, Michael P. Ver Haag, verhaag@uwm.edu1, Jeffrey R. Deschamps2, and James M. Cook, capncook@uwm.edu1. (1) Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, 3210 N. Cramer St., Milwaukee, WI 53211, (2) Laboratory of Structural Matters, Naval Research Laboratory, 4555 Overlook Avenue, Washington, DC 20375
It is well known that Nb-alkyl tryptophan alkyl esters undergo the Pictet-Spengler reaction with aldehydes to furnish both cis- and trans-1,2,3,4-tetrahydro-β-carbolines, with the trans isomer predominating. Epimerization at C-1 takes place under acidic conditions to produce, exclusively, the thermodynamically more stable trans diastereomer potentially through a carbocationic intermediate. It has been shown that electronic effects directed toward C-1 do, in fact, alter the reaction rate of this process. Due to this, rate data was compared to Hammett σ and σ+ values in order to determine if the carbcationic intermediate is involved in this process. Rate data will be presented for a series of 3-substituted 1-phenyl-1,2,3,4-tetrahydro-β-carbolines which contain different levels of electronic character at C-1 in order to apply a linear free energy relationship.
 

Physical Organic Chemistry, Metal-Mediated Reactions, Asymmetric Reactions and Syntheses
8:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster

Division of Organic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007