Synthesis of dihydrouracils spiro-fused to pyrrolidines: druglike molecules based on the 2-arylethyl amine scaffold.

The synthesis of a small library of dihydrouracils spiro-fused to pyrrolidines is described. These compounds are synthesized from beta-aryl pyrrolidines, providing products with the 2-arylethyl amine moiety, a structural feature often encountered in compounds active in the central nervous system. The b-aryl pyrrolidines are synthesized through a three-step methodology that includes a Knoevenagel condensation reaction, a 1,3-dipolar cycloaddition reaction, and a nitrile reduction.

Synthesis of tetrahydro-beta-carbolines and tetrahydroisoquinolines fused to pyrrolidines and solution-phase parallel acylation.

A structurally diverse library of potentially pharmacologically important compounds employing classical synthesis methods is described. These compounds are synthesized from beta-aryl pyrrolidines, providing products with the 2-arylethyl amine moiety, a structural feature often encountered in compounds active in the central nervous system. Tri- and tetracyclic scaffolds were obtained using the Pictet-Spengler reaction, resulting in hexahydropyrrolo[3,4-c]isoquinolines 1-3, an octahydropyrrolo[3',4':5,6]pyrido[3,4-b]indole 4, and a hexahydrofuro[2,3-d]pyrrolo[3,4-b]pyridine 5.

Synthesis of hydantoins and thiohydantoins spiro-fused to pyrrolidines: druglike molecules based on the 2-arylethyl amine scaffold.

The synthesis of a 144-compound library of hydantoins and thiohydantoins spiro-fused to pyrrolidines is described. These compounds are synthesized from beta-aryl pyrrolidines, providing products with the 2-arylethyl amine moiety, a structural feature often encountered in compounds active in the central nervous system. All possible stereoisomers of the two-stereocenter products are synthesized.

Solution-phase parallel annulation of (thio)hydantoins to tetrahydroisoquinolines and tetrahydro-beta-carbolines containing the 2-arylethyl amine scaffold.

The one-step solution-phase parallel synthesis of two structurally diverse libraries of pharmacologically important compounds is described. The presented compounds combine three privileged structures: the 2-arylethyl amine moiety, a tetrahydro(hetero)areno[c]pyridine, and a (thio)hydantoin. These compounds are synthesized by annulation of a hydantoin or a 2-thiohydantoin ring to tri- or tetracyclic scaffolds, containing the 2-arylethyl amine moiety and a tetrahydroisoquinoline, a tetrahydro-beta-carboline, or a tetrahydrofuro[3,2-c]pyridine.

Efficient library synthesis of imidazoles using a multicomponent reaction and microwave irradiation.

Optimization of Radziszewski's four-component reaction employing a microwave-assisted protocol, led to a small library of 48 imidazoles with a success rate of 65% (conversion > 45%). All three diversity points of the four-component reaction were varied. Aromatic and aliphatic inputs were successfully implemented and mono-, di-, tri- and tetrasubstituted imidazoles with various substitution patterns were synthesized.

Synthesis of spirohydantoins and spiro-2,5-diketopiperazines via resin-bound cyclic alpha,alpha-disubstituted alpha-amino esters.

A seven-step solid-phase synthesis of spirohydantoins and an eight-step solid-phase synthesis of spiro-2,5-diketopiperazines is reported. Key intermediate in the synthesis of both compound libraries is the resin-bound cyclic alpha,alpha-disubstituted alpha-amino ester, which can be obtained after selective homogeneous reduction of the aliphatic nitro ester using tin(II) chloride dihydrate. Nitro ester, in turn, is synthesized by a high-pressure-assisted [4 + 2] cycloaddition of resin-bound nitro alkene and butadiene, whereas nitro alkene is obtained by a Knoevenagel condensation of resin-bound nitro acetate with an imine.

Stimulation of liver-directed cholesterol flux in mice by novel N-acetylgalactosamine-terminated glycolipids with high affinity for the asialoglycoprotein receptor.

Objective: Interventions that promote liver-directed cholesterol flux can suppress atherosclerosis, as demonstrated for scavenger receptor-BI overexpression in hypercholesterolemic mice. In analogy, we speculate that increasing lipoprotein flux to the liver via the asialoglycoprotein receptor (ASGPr) may be of therapeutic value in hypercholesterolemia.

Methods And Results: A bifunctional glycolipid (LCO-Tyr-GalNAc3) with a high-nanomolar affinity for the ASGPr (inhibition constant 2.

Dialyzable carbosilane dendrimers as soluble supports for the functionalization of pyridine fragments via palladium-catalyzed coupling reactions.

[reaction: see text] The use of carbosilane (CS) dendrimers as soluble supports in liquid phase organic synthesis (LPOS) is described. Control of the three key steps is perfectly achieved by covalently binding a pyridine fragment to the soluble support, modifying it via coupling reactions, and releasing it at the end. Nanofiltration (dialysis) allows facile purification of the supported molecules after each step.

Design and synthesis of novel N-acetylgalactosamine-terminated glycolipids for targeting of lipoproteins to the hepatic asialoglycoprotein receptor.

A novel glycolipid has been prepared that contains a cluster glycoside with an unusually high affinity for the asialoglycoprotein receptor (ASGPr) and a bile acid moiety that mediates stable incorporation into lipidic particles. The glycolipid spontaneously associated with low-density lipoproteins (LDL) and high-density lipoproteins (HDL) within human and murine plasma, and loading of lipoproteins with this glycolipid resulted in an efficient dose-dependent recognition and uptake of LDL and HDL by the liver (and not by spleen) upon intravenous injection into wild-type mice. Preinjection with asialoorosomucoid largely inhibited the uptake, establishing that both HDL and LDL were selectively recognized and processed by the ASGPr on liver parenchymal cells.

The use of a mannitol-derived fused oxacycle as a combinatorial scaffold.

An efficient and high-yielding solid-phase synthesis of a small library of compounds containing a cis-fused pyranofuran structural motive is described. With use of the cheap and readily available D-(+)-mannitol, a highly functionalized sugar template was synthesized and immobilized on a solid support via an olefinic linker. Modification of this two-point molecular scaffold and subsequent ring-closing metathesis/cleavage gave access to a series of functionalized conformationally constrained fused oxacycles.

Determination of the upper size limit for uptake and processing of ligands by the asialoglycoprotein receptor on hepatocytes in vitro and in vivo.

The asialoglycoprotein receptor (ASGPr) on hepatocytes plays a role in the clearance of desialylated proteins from the serum. Although its sugar preference (N-acetylgalactosamine (GalNAc) >> galactose) and the effects of ligand valency (tetraantennary > triantennary >> diantennary >> monoantennary) and sugar spacing (20 A 10 A 4 A) are well documented, the effect of particle size on recognition and uptake of ligands by the receptor is poorly defined. In the present study, we assessed the maximum ligand size that still allows effective processing by the ASGPr of mouse hepatocytes in vivo and in vitro.

Design and synthesis of a multivalent homing device for targeting to murine CD22.

CD22 is a cell-surface glycoprotein uniquely located on mature B-cells and B-cell derived tumour cells. Current evidence suggests that binding of endogenous ligands to CD22 leads to modulation of B-cell activation by antigen. Incidentally, however, B-cell activation may derail.

A structure-function study of ligand recognition by CD22beta.

B-cell-specific CD22 is a member of a group of cell adhesion molecules within the immunoglobulin superfamily that display binding to glycans with terminal sialic acid residues. Binding of endogenous ligands to CD22 triggers B-cell activation and proliferation. It is therefore conceivable that high affinity ligands for CD22 may be of value as inhibitors of B-cell activation in allergy and chronic inflammation.

Novel hepatotrophic prodrugs of the antiviral nucleoside 9-(2-phosphonylmethoxyethyl)adenine with improved pharmacokinetics and antiviral activity.

The device of new hepatotrophic prodrugs of the antiviral nucleoside 9-(2-phosphonylmethoxyethyl)adenine (PMEA) with specificity for the asialoglycoprotein receptor on parenchymal liver cells is described. PMEA was conjugated to bi- and trivalent cluster glycosides (K(GN)(2) and K(2)(GN)(3), respectively) with nanomolar affinity for the asialoglycoprotein receptor. The liver uptake of the PMEA prodrugs was more than 10-fold higher than that of the parent drug (52+/-6% and 62+/-3% vs.

Synthesis of a lipophilic prodrug of 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and its incorporation into a hepatocyte-specific lipidic carrier.

Purpose: 9-(2-Phosphonylmethoxyethyl)adenine (PMEA), a potent inhibitor of Hepatitis B virus replication, is in vivo hardly taken up by parenchymal liver cells (the site of infection). Our aim is to examine whether lactosylated reconstituted HDL (LacNeoHDL), a lipidic particle that is specifically internalized by parenchymal liver cells, is a suitable carrier for the selective delivery of PMEA to this cell type.

Methods: To incorporate PMEA into LacNeoHDL, we synthesized a lipophilic prodrug (PMEA-LO) by coupling PMEA via an acid-labile phosphonamidate bond to lithocholic acid-3alpha-oleate.

Design and synthesis of novel amphiphilic dendritic galactosides for selective targeting of liposomes to the hepatic asialoglycoprotein receptor.

A series of glycolipids have been prepared which contain a cluster galactoside moiety with high affinity for the hepatic asialoglycoprotein receptor and a bile acid ester moiety which mediates stable incorporation into liposomes. Loading of liposomes with these glycolipids at a ratio of 5% (w/w) resulted in efficient recognition and uptake of the liposomes by the liver. Preinjection with asialofetuin almost completely inhibited the uptake, establishing that the liposomes were selectively recognized and processed by the asialoglycoprotein receptor on liver parenchymal cells.

Preparation of conjugates of oligodeoxynucleotides and lipid structures and their interaction with low-density lipoprotein.

The high expression level of receptors for low-density lipoprotein (LDL) on tumor cells makes LDL an attractive carrier for selective delivery of drugs to these cells. The aim of this study is to allow incorporation of oncogene-directed antisense oligodeoxynucleotides (ODNs) into the lipid moiety of LDL. Therefore, ODNs were conjugated with oleic acid, cholesterol, and several other steroid lipids.

The cyclic diguanylic acid regulatory system of cellulose synthesis in Acetobacter xylinum. Chemical synthesis and biological activity of cyclic nucleotide dimer, trimer, and phosphothioate derivatives.

An unusual compound, cyclic-bis(3'----5') diguanylic acid (c-di-GMP or cGpGp), is involved in the regulation of cellulose synthesis in the bacterium Acetobacter xylinum. This cyclic dinucleotide acts as an allosteric, positive effector of cellulose synthase activity in vitro (Ka = 0.31 microM) and is inactivated via degradation by a Ca2(+)-sensitive phosphodiesterase, PDE-A (Km = 0.

Cyclic diguanylic acid behaves as a host molecule for planar intercalators.

Cyclic ribodiguanylic acid, c-(GpGp), is the endogenous effector regulator of cellulose synthase. Its three-dimensional structure from two different crystal forms (tetragonal and trigonal) has been determined by X-ray diffraction analysis at 1 A resolution. In both crystal forms, two independent c-(GpGp) molecules associate with each other to form a self-intercalated dimer.

Synthesis of cyclic oligonucleotides by a modified phosphotriester approach.

Evidence will be presented to show that the allyl group is suitable for the protection of a 3'-terminal phosphodiester function. The latter will be demonstrated by the synthesis, via a phosphotriester approach, of two cyclic tetraribonucleotides [r(AAAA) and r(UAMe2UAMe2)], two cyclic hexadeoxyribonucleotides [d(CGCGCG) and d(TAAAAA)] and a cyclic octadeoxyribonucleotide [d(CGTGCGTG)].