Di-tsopropyl phosphorofluoridate

With lower concentrations, the inhibition produced varied with the time of incubation. Fig. 12 shows the inhibition of cholinesterase by di-tsopropyl phosphorofluoridate, and by a comparable amount of eserine, after varying times. The action of eserine reaches a maximum within 5 min., while the inhibition by phosphorofluoridate is initially less rapid, but is progressive and ultimately more complete. The latter effect suggests an irreversible inactivation of the enzyme rather than an equilibrium. 

Fig. 14. Inhibition of horse-serum cholinesterase by various compounds. Incubated for 15 min. at 20° before addition of 2 mg. of acetylcholine chloride. A, di-tsopropyl phosphorofluoridate B, disec.-butyl phosphorofluoridate C, eserine D, diphenyl phosphorofluoridate E, dithioethyl phosphorofluoridate F, tetramethylphosphorodiamidic fluoride O, diethyl -methylphosphor-amidate.

The individual stages having been established, the whole process was then re-examined with a view to preparing di-tsopropyl phosphorofluoridate on a technical scale. As a result of many... 

We found that the toxicity and myotic activity of di-taopropyl phosphorofluoridate (XI) were far greater than that of di-n-propyl phosphorofluoridate. In Report no. 6 on fluoro-phosphonates to the Ministiy of Supply we described the preparation of di-sec.-biUyl phosphorcfluoridate (XII) by the hydrogen phosphite method (p. 6). The compound was found to be very toxic and to produce severe myosis in man and ani-mab. The symptoms displayed during and after exposure were identical with those produced by di-tsopropyl phosphorofluoridate. The L.c. 50 for di-sec.-butyl phosphorofluoridate for mice for deaths within 2 hr. was 0-6 mg./l., and that for deaths within 48 hr. was 0-54 mg./l. 

It has been reported that cholinesterase inhibitors (such as di-tsopropyl phosphorofluoridate) increase the permeabihly of squid giant axons towards sodium and potassium. There is also an indication that the erythrocyte requires, among othw factors, an adequate acetylcholine-cholinesterase system to prevent a gain of sodium or a loss of potassium. The conclusion that permeability is dependent on cholinesterase activity, however, seems to be contested by Strickland and Thompson. ... 

Di-iaopropyl phosphorofluoridate. Phosphorus oxydichlorofluoride (50 g.) is dissolved in dry ether (100 c.c.), tsopropyl alcohol (dried over calcium oxide 50 g., 15 per cent excess) in dry ether (100 c.c.) is added slowly with cooling, and the mixture kept for 1 hr. Dry ammonia is then passed through the liquid, with cooling. The liquid... 

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