STEREOCHEMISTRY OF THE INHIBITION OF DELTA-CHYMOTRYPSIN WITH OPTICALLY-ACTIVE CIS-DECALINE-TYPE ORGANOPHOSPHATES - P-31-NMR STUDIES

Investigation of the inhibition of delta-chymotrypsin with the four no vel, optically active, axially and equatorially substituted cis-3-(2,4 -dinitrophenoxy)-2,4-dioxa-3 lambda(5)-phosphabicyclo[4.4.0]decan-3-on es (= trophenoxy)hexahydro-4H-1,3,2-benzodioxaphosphorin 2-oxides) sho wed only the equatorially substituted enantiomer (-)-4b to be an irrev ersible inhibitor of the enzyme. P-31-NMR Spectroscopic monitoring of the inhibition of stoichiometric amounts of the enzyme and (-)-4b at p H 7.8 revealed a quickly rising resonance at - 2.49 ppm assigned to th e hydrolysis product 8 and later, while inhibition proceeded, a second one at - 4.08 ppm, attributed to the delta-chymotrypsin adduct 7 (Sch eme 3). Comparison of the latter signal with the P-31-NMR chemical shi fts of the covalent phosphoserine model compounds (-)-6a (-5.67 ppm, a xial substitution) and (+)-6b (-4.02 ppm, equatorial substitution) sug gests that the inhibition proceeded via near retention of the configur ation at the P-atom of (-)-4b yielding the equatorially substituted co valent Ser(195) adduct 7.