Synthesis and kinetic analysis of some phosphonate analogs of cyclophostin as inhibitors of human acetylcholinesterase

Abstract

Two new monocyclic analogs of the natural AChE inhibitor cyclophostin and two exocyclic enol phosphates were synthesized. The potencies and mechanisms of inhibition of the bicyclic and monocyclic enol phosphonates and the exocyclic enol phosphates toward human AChE are examined. One diastereoisomer of the bicyclic phosphonate exhibits an IC50 of 3 μM. Potency is only preserved when the cyclic enol phosphonate is intact and conjugated to an ester. Kinetic analysis indicates both a binding and a slow inactivation step for all active compounds. Mass spectrometric analysis indicates that the active site Ser is indeed phosphorylated by the bicyclic phosphonate.

Rat hormone sensitive lipase inhibition by cyclipostins and their analogs

“…As stated in the introduction, we have previously shown that cyclophostin inhibits AChE irreversibly [8]. Since the basic chemistry should be the same, we expect cyclipostin to inhibit HSL irreversibly.…”

“…The synthesis of the monocyclic phosphonates ( 7, 8, 9a, 10a, 10b, 11a, 11b, 12a, 12b ) also followed published procedures [8, 26]. …”

“…The basic structure is represented by cyclophostin 1a (Scheme 1), a bicyclic phosphate isolated from Streptomyces species strain DSM 13381 [6]. As we have recently characterized, this compound is a potent (nanomolar) irreversible inhibitor of AChE [7, 8]. Much like the chemical warfare agents Sarin and V/X [9], it targets the conserved Ser residue in the catalytic triad of this enzyme through phosphorylation.…”

“…Much like the chemical warfare agents Sarin and V/X [9], it targets the conserved Ser residue in the catalytic triad of this enzyme through phosphorylation. We recently demonstrated that bicyclic phosphonate analogs ( 2a, 2b ) of cyclophostin are less potent AChE inhibitors than the natural product [8]. Monocyclic phosphonate analogs (large phosphate ring) are as potent as the corresponding bicyclic phosphonate.…”

“…The long hydrocarbon tails suggest a substrate-type binding mode. Cyclophostins share the cyclic phosphate electrophilic center of cyclipostins, which have already been shown to irreversibly modify the active site Ser of AChE [8] and microbial lipases [26]. We recently reported the synthesis of cyclipostin P ( 4a, 4b ) [27].…”