Synthesis of D- and L-myo-inositol 1,2,4,6-tetrakisphosphate, regioisomers of myo-inositol 1,3,4,5 tetrakisphosphate: activity against Ins(1,4,5)P3 binding proteins.
We report here the synthesis of D- and L-myo-inositol 1,2,4,6-tetrakisphosphate 3a and 3b and the racemic modification 3ab. Racemic myo-inositol 1,2,4,6-tetrakisphosphate 3ab was synthesised from DL-1,2,4,6-tetra-O-allyl-myo-inositol 9ab. Benzylation and de-allylation provided the tetraol 11ab, which was phosphitylated in the presence of bis(benzyloxy)diisopropylaminophosphine and 1H-tetrazole, then oxidised to give the fully protected 1,2,4,6-tetrakisphosphate 13ab. Hydrogenolysis of 13ab and purification of product by ion exchange chromatography gave racemic myo-inositol 1,2,4,6-tetrakisphosphate 3ab, which showed no demonstrable agonism or antagonism for Ca2+ release at 200 microM in permeabilised hepatocytes. The chiral derivatives, D-3a and L-myo-inositol 1,2,4,6-tetrakisphosphate 3b were synthesised from 5-O-benzyl-1,4,6-tri-O-p-methoxybenzyl-myo-inositol 19ab, which was resolved using R-(-)-O-acetylmandelic acid providing two diastereoisomers 21 and 22 which were separated and deacylated to give the corresponding enantiomers. Further transformations gave the corresponding chiral 1,2,4,6-tetraols which were phosphitylated, oxidised, deprotected and purified as for the racemic mixture. The enantiomeric tetrakisphosphates 3a and 3b were evaluated for inhibition of the metabolic enzymes inositol 1,4,5-trisphosphate 5-phosphatase and 3-kinase in comparison with the enantiomers of another synthetic regioisomer D- and L-myo-inositol 1,2,4,5-tetrakisphosphate. Both D- and L-myo-inositol 1,2,4,6-tetrakisphosphate inhibit 5-phosphatase with an IC50 value of 3.8 microM and 14 microM, repectively. However, both enantiomers were poorly recognised by the 3-kinase enzyme, with IC50 values greater than 100 microM. The enantiomers of the 1,2,4,5-tetrakisphosphate showed the same relative pattern of activity towards the two enzymes but were more potent against 5-phosphatase (0.47 microM and 3 microM respectively).
Wolfson Laboratory of Medicinal Chemistry, Department of Pharmacy and Pharmacology, University of Bath, Claverton Down, Bath, UK BA2 7AY.
Stephen J
SJ
Mills
Katrien
K
Backers
Christophe
C
Erneux
Barry V L
BV
Potter
D000818:Animals; D001921:Brain / Q000201:enzymology; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000737:chemistry*; D006801:Humans; D007295:Inositol Phosphates / Q000737:chemistry*; D000072181:Inositol Polyphosphate 5-Phosphatases; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors; D011485:Protein Binding; D051381:Rats; D013237:Stereoisomerism
D004791:Enzyme Inhibitors; D007295:Inositol Phosphates; C116606:inositol-1,2,4,5-tetrakisphosphate; C081655:inositol-1,3,4,5-tetrakisphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases