Synthesis of 1,3,3-trimethyl- and 1,2,3,3-tetramethyl-5-(methyl- and dimethyl-carbamoyloxy) indolines and their methiodides

Cholinesterase studies with (R) (+)- and (S)(-)-5-(1,3,3-trimethylindolinyl)-N-(1-phenylethyl)carbamate

A limited number of carbamates have been found useful for treatment of cholinergic symptoms with pyridostigmine and physostigmine being the main focus. In recent years 5-(1,3,3-trimethylindolinyl)N,N-dimethylcarbamate (I) has received considerable attention in the Chinese literature for a similar role. We report on the first synthesis of stereoisomers of an analog of (I). The isomers prepared were (R)(+)-5-(1,3,3-trimethylindolinyl)-N-(1-phenylethyl)carbamate (II) and (S)(-)-5-(1,3,3-trimethylindolinyl)-N-(1-phenylethyl)carbamate (III). The pKa value for each isomer was 6.8. Eel acetylcholinesterase inhibition studies were carried out at 25.0 degrees C over the pH range of 6.0 to 9.0. They reflect the first pH profiles using enantiomorphs of a cholinesterase inhibitor. The inhibition potencies for (II) and (III) over the range examined were similar. At pH 7.60 the ki for II = 7.38 x 10(3) M-1 min-1 (SD = 398) and for (III) the ki = 6.67 x 10(3) M-1 min-1 (SD = 355). In accord with the findings of Wilson and Bergmann20 on physostigmine our results indicate that the protonated form of (II) and (III) is the more potent inhibitor.

Anticholinesterase activity of potential therapeutic 5-(1,3,3-trimethylindolinyl) carbamates

Six N-alkyl and N-aryl 5-(1,3,3-trimethylindolinyl) carbamates were synthesized and studied for their structure-activity relationships in inhibiting eel acetylcholinesterase (AChE). The carbamates were 5-(1,3,3-trimethylindolinyl)N,N-dimethylcarbamate (Cui Xing Ning) (I), 5-(1,3,3-trimethylindolinyl)N,N-diethylcarbamate (IV), 5-(1,3,3-trimethylindolinyl)N-ethylcarbamate (III), 5-(1,3,3-trimethylindolinyl)N,N-diethylcarbamate (IV), 5-(1,3,3-trimethylindolinyl)N-heptylcarbamate (V), and 5-(1,3,3-trimethylindolinyl)N-(3-chlorophenyl)carbamate (VI). The inhibition studies were carried out at 25.0 degrees C at pH 7.60. The rank order of the ki values for eel AChE inhibition is II > V > I > III > VI > IV. Compound II has a greater affinity for the enzyme than any irreversible inhibitor cited in the literature (Kd = 7.14 x 10(-8) M). Our findings should aid in the application of these carbamates (1) for counteracting the cholinergic problems associated with various diseases, and (2) for developing potential pretreatment compounds for organophosphate poisoning.

The synthesis and anti-acetylcholinesterase activities of (plus)-physostigmine and (plus)-physovenine

(+)-Physostigmine and (+)-physovenine have been synthesized. The anti-acetylcholinesterase activities of these two bases, which have been investigated in vitro using erythrocyte acetylcholinesterase, have been found to be much lower than the corresponding activities of the alkaloids (-)-physostigmine and (-)-physovenine. Possible reasons for these activity differences are discussed.