(A) Synthesis of G-Paro (G-Kana followed analogous procedures): (a) 1,3-di-Boc-2-(trifluoromethylsulfonyl)guanidine, triethylamine, 5:1 dioxane:water, rt, 3 days; (b) HCl, ethyl acetate, rt, 4 h. (B) PCA plot of RNA training set with expanded aminoglycoside receptor library. A total of nine commercially available aminoglycosides and 2 guanidino-aminoglycosides were used as receptors. Ovals indicate 95% confidence intervals for each cluster.