FIGURE 1:
Fractionation and structural assignment of NO2-LA regioisomers. (A) Shown is a representative preparative scale HPLC elution profile of the mixture of NO2-LA regioisomers synthesized as described in Experimental Procedures. Elutions were monitored at 274 nm. Integration of the peak areas indicated that the relative ratio of fractions (fx) 1, 2, and 3 was ~1:1:2. (B) Structures assigned by NMR analysis to the three fractions (see the text and Supporting Information).