. Author manuscript; available in PMC: 2008 Nov 5.

Published in final edited form as: Tetrahedron. 2007 Nov 5;63(45):11030–11039. doi: 10.1016/j.tet.2007.08.041

Table 2.

Concentration dependence of pyrrole and lactam NH chemical shifts of 1 in (CD₃)₂SO and in CDCl₃ at 22°C compared with similar data for methyl xanthobilirubinate (XBR-Me).

Pyrrole (P) and Lactam (L) Chemical Shifts (δ, ppm)

Conc. of 1 (mM)	(CD₃)₂SO		Conc of 1 (mM)	CDCl₃		Conc. of XBR-Me (mM)	CDCl₃
Conc. of 1 (mM)	PNH	LMH	Conc of 1 (mM)	PNH	LNH	Conc. of XBR-Me (mM)	PNH	LNH
0.8907	10.084	10.215	0.8172	9.712	10.302	0.9766^a	10.136	10.933^a
0.4453	10.084	10.215	0.4086	9.686	10.283	0.4883	10.048	10.765
0.2227	10.084	10.215	0.2643	9.662	10.257	0.1808	9.700	10.371
0.0445	10.084	10.215	0.0409	9.584	10.186	0.09039	9.535	10.200

The data plateau at higher concentrations, 0.125 M; PNH: 10.401, LNH: 11.334.