Table 1. Caco-2 permeability of compound 6a.

Compound	A–B permeability a (Caco-2, cm s–1) (10–6)	B–A permeability a (Caco-2, cm s–1) (10–6)	Papp (B–A)/Papp (A–B)
6a	19.73	21.81	1.11
NAC	<1.09 b	<0.61 b	N/A

^aEach value is an average of n = 3, measured at c = 10 μM.

^bPapp values were expressed as “<” the values that were calculated using the minimum concentration of the standards for receiver sides due to the fact that the real concentrations in the receivers were below quantification limit (BQL).