In vitro and in situ experimental models that are descriptive of drug absorption in vivo are valuable tools in the discovery of new chemical entities that are bioavailable after oral administration. The specific objective of the study was to compare the intestinal permeabilities obtained in the three absorption models for consistency, and to assess the utility of the models in predicting the fraction of dose absorbed in human studies. The intestinal absorption models that were compared are widely used: the rat in situ single-pass intestinal perfusion system, the rat everted intestinal ring method, and monolayers of human colon adenocarcinoma cell line (CACO-2). The models were compared using small molecular reference compounds, as well as a series of peptidomimetic (PM) analogs. Each model had strong potential for estimating the fraction absorbed. For small organic molecules, excellent correlation was observed when permeabilities from CACO-2 cells and perfusions, or everted rings and perfusions, were compared. Weaker correlation was observed between everted rings and CACO-2 cells. Permeabilities for the set of reference compounds and PMs were positively correlated between any two of the three systems. Variance between correlations for reference compounds and PMs are likely due to structural features and physicochemical properties that are unique to the latter class of compounds. The results support caution in extrapolating correlations based on findings with small organic molecules to the behavior of complex peptidomimetics. Corroboration of permeabilities with two methods of determination is a useful cross-validation of experimental systems, as well as producing a reliable permeability assessment.(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract

A highly efficient one-pot procedure for 3-sulfenylation of 2-carboxyindoles is described. Treatment of thiols with N-chlorosuccinimide at -78 degrees C in CH(2)Cl(2) affords sulfenyl chlorides in situ that readily react with 2-carboxyindoles to give 3-thioindoles in high yields. This new method is milder, produces less waste, and is compatible with a wide range of thiol and indole functionality. [reaction: see text]

The 4-hydroxy-5,6-dihydropyrone template was utilized as a flexible scaffolding from which to build potent active site inhibitors of HIV protease. Dihydropyrone 1c (5,6-dihydro-4-hydroxy-6-phenyl-3-[(2-phenylethyl)thio]-2H-pyran-2-one) was modeled in the active site of HIV protease utilizing a similar binding mode found for the previously reported 4-hydroxybenzopyran-2-ones. Our model led us to pursue the synthesis of 6,6-disubstituted dihydropyrones with the aim of filling S1 and S2 and thereby increasing the potency of the parent dihydropyrone 1c which did not fill S2. Toward this end we attached various hydrophobic and hydrophilic side chains at the 6-position of the dihydropyrone to mimic the natural and unnatural amino acids known to be effective substrates at P2 and P2'. Parent dihydropyrone 1c (IC50 = 2100 nM) was elaborated into compounds with greater than a 100-fold increase in potency [18c, IC50 = 5 nM, 5-(3,6-dihydro-4-hydroxy-6-oxo-2-phenyl-5-[2-phenylethyl)thio] -2H-pyran-2-yl)pentanoic acid and 12c, IC50 = 51 nM, 5,6-dihydro-4-hydroxy-6-phenyl-6-(2-phenylethyl)-3- [(2-phenyl-ethyl)thio]-2H-pyran-2-one]. Optimization of the 3-position fragment to fill S1' and S2' afforded potent HIV protease inhibitor 49 [IC50 = 10 nM, 3-[(2-tert-butyl-5-methylphenyl)sulfanyl]-5,6-dihydro-4 -hydroxy-6-phenyl-6-(2-phenylethyl)-2H-pyran-2-one]. The resulting low molecular weight compounds (< 475) have one or no chiral centers and are readily synthesized.

No abstract