Syntheses of two enantiomeric pairs of myo-inositol(1,2,4,5,6) and -(1,2,3,4,5) pentakisphosphate

Lead-Catalyzed Aqueous Benzoylation of Carbohydrates with an Acyl Phosphate Ester

Biochemical systems utilize adenylates of amino acids to aminoacylate the 3'-terminal diols of tRNAs. The reactive acyl group of the biological acylation agent is a subset of the general class of acyl phosphate monoesters. Those compounds are relatively stable in aqueous solutions, and their alkyl esters are conveniently prepared. It has previously been shown that biomimetic reactions of acyl phosphate monoesters with diols and carbohydrates are promoted by lanthanide salts. However, they also promote hydrolysis of acyl phosphate reagents, and the overall yields are modest. An assessment of the catalytic potential of alternative Lewis acids reveals that lead ions may be more effective as catalysts than lanthanides. Treatment of carbohydrates with benzoyl methyl phosphate (BMP) and triethylamine in water with added lead nitrate produces monobenzoyl esters in up to 75% yield. This provides a water-compatible pathway for novel patterns of benzoylation of polyhydroxylic compounds.

Comparative Mechanistic and Substrate Specificity Study of Inositol Polyphosphate 5-Phosphatase Schizosaccharomyces pombe Synaptojanin and SHIP2

Inositol-5-phosphatases are important enzymes involved in the regulation of diverse cellular processes from synaptic vesicle recycling to insulin signaling. We describe a comparative study of two representative inositol-5-phosphatases, Schizosaccharomyces pombe synaptojanin (SPsynaptojanin) and human SH2 domain-containing inositol-5-phosphatase SHIP2. We show that in addition to Mg2+, transition metals such as Mn2+, Co2+, and Ni2+ are also effective activators of SPsynaptojanin. In contrast, Ca2+ and Cu2+ are inhibitory. We provide evidence that Mg2+ binds the same site occupied by Ca2+ observed in the crystal structure of SPsynaptojanin complexed with inositol 1,4-bisphosphate (Ins(1,4)P2). Ionizations important for substrate binding and catalysis are defined for the SPsynaptojanin-catalyzed Ins(1,4,5)P3 reaction. Kinetic analysis with four phosphatidylinositol lipids bearing a 5-phosphate and 54 water-soluble inositol phosphates reveals that SP-synaptojanin and SHIP2 possess much broader substrate specificity than previously appreciated. The rank order for SPsynaptojanin is Ins(2,4,5)P3 > phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) approximately Ins(4,5)P2 approximately Ins(1,4,5)P3 approximately Ins(4,5,6)P3 > PtdIns(3,5)P2 approximately PtdIns(3,4,5)P3 approximately Ins(1,2,4,5)P4 approximately Ins(1,3,4,5)P4 approximately Ins-(2,4,5,6)P4 approximately Ins(1,2,4,5,6)P5. The rank order for SHIP2 is Ins(1,2,3,4,5)P5 > Ins(1,3,4,5)P4 > PtdIns(3,4,5)P4 approximately PtdIns(3,5)P2 approximately Ins(1,4,5,6)P4 approximately Ins(2,4,5,6)P4. Because inositol phosphate isomers elicit different biological activities, the extended substrate specificity for SPsynaptojanin and SHIP2 suggest that these enzymes likely have multiple roles in cell signaling and may regulate distinct pathways. The unique substrate specificity profiles and the importance of 2-position phosphate in binding also have important implications for the design of potent and selective SPsynaptojanin and SHIP2 inhibitors for pharmacological investigation.

Monoesterification of di-O-isopropylidene and di-O-cyclohexylidene chiro-inositols

Monoesterification of D- or L-chiro-inositols protected as diacetals proceeds in excellent selectivity and yields. The metal-catalyzed, one-step reaction proceeds at room temperature under an air atmosphere and has been developed using a range of examples.