Synthesis and binding studies of an optically pure hexadeoxy-1,4,5-tris(methylenesulfonic acid) analogue of IP3

Stereoselective synthesis of a 4-⍺-glucoside of valienamine and its X-ray structure in complex with Streptomyces coelicolor GlgE1-V279S

Glycoside hydrolases (GH) are a large family of hydrolytic enzymes found in all domains of life. As such, they control a plethora of normal and pathogenic biological functions. Thus, understanding selective inhibition of GH enzymes at the atomic level can lead to the identification of new classes of therapeutics. In these studies, we identified a 4-⍺-glucoside of valienamine (8) as an inhibitor of Streptomyces coelicolor (Sco) GlgE1-V279S which belongs to the GH13 Carbohydrate Active EnZyme family. The results obtained from the dose-response experiments show that 8 at a concentration of 1000 µM reduced the enzyme activity of Sco GlgE1-V279S by 65%. The synthetic route to 8 and a closely related 4-⍺-glucoside of validamine (7) was achieved starting from readily available D-maltose. A key step in the synthesis was a chelation-controlled addition of vinylmagnesium bromide to a maltose-derived enone intermediate. X-ray structures of both 7 and 8 in complex with Sco GlgE1-V279S were solved to resolutions of 1.75 and 1.83 Å, respectively. Structural analysis revealed the valienamine derivative 8 binds the enzyme in an E₂ conformation for the cyclohexene fragment. Also, the cyclohexene fragment shows a new hydrogen-bonding contact from the pseudo-diaxial C(3)-OH to the catalytic nucleophile Asp 394 at the enzyme active site. Asp 394, in fact, forms a bidentate interaction with both the C(3)-OH and C(7)-OH of the inhibitor. In contrast, compound 7 disrupts the catalytic sidechain interaction network of Sco GlgE1-V279S via steric interactions resulting in a conformation change in Asp 394. These findings will have implications for the design other aminocarbasugar-based GH13-inhibitors and will be useful for identifying more potent and selective inhibitors.

Synthesis of 3-Position-Modified Analogues of myo-Inositol 1,4,5-Trisphosphate, Tools for Investigation of the Polyphosphoinositide Pathway of Cellular Signaling

Methods for the synthesis of 3-O-(carboxymethyl)- and 3-O-alkylated myo-inositol 1,4,5-trisphosphates in racemic form from myo-inositol have been devised. For DL-3-O-(carboxymethyl)-myo-inositol 1,4,5-trisphosphate, an analogue of myo-inositol 1,3,4,5-tetrakisphosphate, DL-3-O-allyl-2,6-di-O-benzyl-1-O-(p-methoxybenzyl)-4,5-O-isopropylidene-myo-inositol (14) was prepared from myo-inositol in seven steps. The triol DL-3-O-allyl-2,6-di-O-benzyl-myo-inositol (26), which was obtained after treatment of 14 with acid, was phosphitylated and the product oxidized to give the fully protected trisphosphate 27. The efficient oxidative cleavage of the 3-O-allyl ether of 27 in the presence of the cyanoethyl-protected phosphate triesters was achieved by treatment of 27 with NaIO(4)/RuCl(3).hydrate to afford the fully protected 3-O-(carboxymethyl) trisphosphate 28. After deblocking, DL-3-O-(carboxymethyl) trisphosphate 6 was obtained. For DL-3-O-alkylated myo-inositol 1,4,5-trisphosphate analogues, the fully protected 14 was isomerized to the cis-prop-1-enyl derivative 15. The propenyl group was removed to give DL-2,6-di-O-benzyl-1-O-(p-methoxybenzyl)-4,5-isopropylidene-myo-inositol (16). The 3-O-methyl ether 17, 3-O-ethyl ether 18, and 3-O-n-propyl ether 19 derivatives were synthesized by treatment of the anion of 16 with methyl iodide, ethyl iodide, or n-propyl iodide, respectively. Removal of the isopropylidene and p-methoxybenzyl groups afforded 3-O-alkylated triols 20, 21, or 22, which were phosphitylated and the products oxidized to give the respective fully protected 3-O-alkylated trisphosphates 23-25. Deprotection furnished 3-O-methyl- (3), 3-O-ethyl- (4), or 3-O-n-propyl-myo-inositol 1,4,5-trisphosphate (5). These compounds will be useful pharmacological tools to explore the interaction of myo-inositol 1,4,5-trisphosphate with its receptor and metabolic enzymes.

ASYMMETRIC DIELS-ALDER REACTION : CIS-1-ARYLSULFONAMIDO-2-INDANOLS AS HIGHLY EFFECTIVE CHIRAL AUXILIARIES

Lewis acid promoted Diels-Alder reaction of acrylate esters of cis-1-arylsulfonamido-2-indanols and cyclopentadiene provided exclusively endo-adducts with high endo-diastereoselectivities.