Two diastereomers of a phosphonate analog 6 of the AChE inhibitor
May 4, 2017
Two diastereomers of a phosphonate analog 6 of the AChE inhibitor cyclophostin were synthesized. from a fermentation solution of (strain NK901093) during a search for natural insecticides.1 The natural product 1 showed potent inhibition of acetyl cholinesterase (AChE) from housefly (CSMA strain) and the brown plant hopper with reported IC50 of 7.6 ×10?10 M. The structure of cyclophostin was first assigned by spectroscopic methods and then confirmed by single crystal X-ray diffraction studies as a bicyclic structure with a seven-membered cyclic enol-phosphate triester fused to a butyrolactone ring. There are chiral centers at both C3a and the AS703026 phosphorus atom. The absolute configurations of the chiral centers were determined to be 3aby the anomalous scattering method. The unusual bicylic enolphosphate is found in some related natural compounds 2 and 3 and the enolphosphate moiety adjacent to a carbonyl is also found in the synthetic insecticides monocrotphos 4 and phosphamidan 5.2-4 The unnamed tetrahydrofuran fused enolphosphates 2a and 2b were isolated during an earlier search for insecticides and were shown to be AChE inhibitors.3 The cyclipostins 3 posses a core structure similar to that of cyclophostin but differ in the phosphate ester.4 The cyclipostins 3 are phosphate esters of long chain lypophilic alcohols of various lengths and structures and all are potent inhibitors of hormone sensitive lipase.4 AChE has been identified as a therapeutic target for myasthenia gravis 5 glaucoma6 and Alzheimer’s disease7 and is well known as the target for insecticides and “nerve gas” chemical warfare agents. The exact mode of inhibition of AChE by cyclophostin has not been reported. Since other phosphate inhibitors of AChE are known to form AS703026 a covalent bond between the phosphorus and the serine residue of enzyme active site it is likely that the mode of inhibition by cyclophostin involves similar kind of interaction (Figure 2). It is also probable that the enolphosphate acts as a leaving group on reaction with the active site serine. Figure 2 Proposed Reaction with the Active Site Serine and a Phosphonate Analog of Cyclophostin Phosphonate analogs of biologically active phosphates have been shown to be an extremely useful tool in investigating mechanistic detail of various enzymatic systems.8 This success is usually attributed to the non-hydrolyzability of a P-C bond (phosphonate analog) when compared to the P-O bond of the corresponding phosphate leading to enhanced compound lifetime in vivo. It should be AS703026 possible to replace the noncritical oxygen at position 5 AS703026 in cyclophostin (and the cyclipostins) with a methylene and still retain the AChE inhibitory activity (Figure 2) whereas loss of the enol oxygen (position 7) should eliminate activity. Herein we report the synthesis of the first phosphonate analog 6 of cyclophostin. Results and Discussion A retrosynthetic analysis of the bicyclic phosphonate 6 suggested that either the lactone or AS703026 the enol phosphonate bond could be formed first giving rise to intermediates 7 and 8 respectively. The common intermediate 9 could be formed a palladium catalyzed substitution reaction of the carbonate derivative 10 of an allylic hydroxy phosphonate with an acetoacetate ester. We reported the use of a similar strategy for the synthesis of the lignan enterolactone.9 It is now well established that allylic hydroxy phosphonate derivatives can be used as intermediates in the synthesis of γ-substituted vinyl phosphonates by 1 3 of functionality.10-12 Following the original work of Zhu and Lu 11 we reported that the facile addition of soft nucleophiles to optically pure carbonate derivatives proceeded with complete transfer of chirality.9 12 Rabbit polyclonal to ZNHIT1.ZNHIT1 (zinc finger, HIT-type containing 1), also known as CG1I (cyclin-G1-binding protein 1),p18 hamlet or ZNFN4A1 (zinc finger protein subfamily 4A member 1), is a 154 amino acid proteinthat plays a role in the induction of p53-mediated apoptosis. A member of the ZNHIT1 family,ZNHIT1 contains one HIT-type zinc finger and interacts with p38. ZNHIT1 undergoespost-translational phosphorylation and is encoded by a gene that maps to human chromosome 7,which houses over 1,000 genes and comprises nearly 5% of the human genome. Chromosome 7 hasbeen linked to Osteogenesis imperfecta, Pendred syndrome, Lissencephaly, Citrullinemia andShwachman-Diamond syndrome. The deletion of a portion of the q arm of chromosome 7 isassociated with Williams-Beuren syndrome, a condition characterized by mild mental retardation, anunusual comfort and friendliness with strangers and an elfin appearance. 4 and 4-(isomer was more active than isomer against AChE from two sources. Since the natural product has the configuration the unnatural isomer may well prove more potent. We are currently pursuing a synthesis of both isomers of the natural product. Experimental section Dimethyl [1-(methoxycarbonyloxy)-4-(benzyloxy)-2-butenyl]phosphonate 10a To a mixture of dimethyl phosphite (8.2 mL 89 mmol) and aldehyde 12a13a (9.2 g 52.