A concise synthesis of spirotryprostatin A

The preparation of two new synthons, 2,5- and 2,6-dibromotryptophan esters, and their use in diastereoselective intramolecular N-acyliminium ion spirocyclization methodology for the rapid construction of spirotryprostatin A and analogues are described.     

Reactions of [(eta(6)-arene)RuCl(2)](2) with Aromatic Phosphines Containing Methoxy Groups in 2,6-Positions

Reactions of [(eta(6)-arene)RuCl(2)](2) 1 (arene = p-cymene (a), 1,2,3,4-Me(4)C(6)H(2) (b), 1,2,3-Me(3)C(6)H(2) (c)) with tris(2,6-dimethoxyphenyl)phosphine (TDMPP) led to loss of two molecules of CH(3)Cl to give (eta(6)-arene)Ru[{2-O-C(6)H(3)-6-OMe}(2){C(6)H(3)(OMe)(2)-2,6}], 2a-c, which contains a trihapto ligand (eta(3)-P,O,O) derived from TDMPP, whereas the 1,3,5-Me(3)C(6)H(3) (1d), 1,2,3,5-Me(4)C(6)H(2) (1e), and C(6)Me(6) (1f) complexes did not react with TDMPP. The structures of 2a and 2b were confirmed by X-ray analyses: for 2a, a = 11.691(2) ?, b = 15.228(2) ?, c = 10.320(1) ?, alpha = 95.93(1) degrees, beta = 113.783(9) degrees, gamma = 83.86(1) degrees, triclinic, P&onemacr;, Z = 2, R = 0.051; for 2b, a = 17.79(2) ?, b = 15.43(1) ?, c = 20.93(1) ?, beta = 91.25(8) degrees, monoclinic, P2(1)/n, Z = 8, R = 0.056. Bis(2,6-dimethoxyphenyl)phenylphosphine (BDMPP) reacted with 1a, 1b, and 1d at room temperature to give (eta(6)-arene)RuCl[PPh(2-O-C(6)H(3)-6-OMe){C(6)H(3)(OMe)(2)-2,6}], 3a,b,d, which contains a dihapto (eta(2)-P,O) ligand derived from BDMPP by an X-ray analysis of 3a: a = 12.33(1) ?, b = 14.246(8) ?, c = 11.236(9) ?, alpha = 91.47(8) degrees, beta = 117.28(6) degrees, gamma = 111.70(6) degrees, triclinic, P&onemacr;, Z = 2, R = 0.040. A similar reaction with 1f recovered the starting materials, but that in refluxing MeCN produced [(eta(6)-C(6)Me(6))Ru[PPh(2-O-C(6)H(3)-6-OMe}(2)], 4f, containing a trihapto (eta(3)-P,O,O) ligand derived from BDMPP. Complex 1d reacted with BDMPP at reflux in MeCN/CH(2)Cl(2) and resulted in a loss of an arene ring to give a five-coordinate complex, Ru[eta(2)-P,O-PPh(2-O-C(6)H(3)-6-OMe){C(6)H(3)(OMe)(2)-2,6}](2)(MeCN), 5. Treatment of (2,6-dimethoxyphenyl)diphenylphosphine (MDMPP) with 1f gave (eta(6)-C(6)Me(6))RuCl[eta(2)-P,O-PPh(2)(2-O-C(6)H(3)-6-OMe)],6f, and that with 1b gave (eta(6)-1,2,3,4-Me(4)C(6)H(2))RuCl[eta(2)-P,O-PPh(2)(2-O-C(6)H(3)-6-OMe}], 6b, and (eta(6)-1,2,3,4-Me(4)C(6)H(2))RuCl(2)[eta(1)-P-PPh(2){C(6)H(3)(OMe)(2)-2,6}],7b. The phosphine ligand of 6b acted as a bidentate ligand derived from MDMPP: a = 8.074(4) ?, b = 16.816(3) ?, c = 18.916(4) ?, beta = 94.05(3) degrees, monoclinic, P2(1)/n, Z = 4, R = 0.051. Transformation of 7b to 6b readily occurred accompanying an elimination of MeCl. Reaction of 1a with MDMPP eliminated an arene ring to give the octahedral compound RuCl(2)[eta(2)-P,OMe-PPh(2){C(6)H(3)(MeO)(2)-2,6}](2), 8. An X-ray analysis of 8 showed that two MDMPP ligands were in a cis-position: a = 10.596(14) ?, b = 27.586(12) ?, c = 13.036(8) ?, beta = 108.17(7) degrees, monoclinic, P2(1)/n, Z = 4, R = 0.035.     

Liquid-Liquid Extraction and Liquid Chromatographic Studies on Interactions of Inorganic Anions with Coordinatively Unsaturated Copper(II) Complexes of Heterocyclic Azo Compounds

The interactions between Cu(II) complexes with heterocyclic azo compounds and several anions were studied by equilibrium analysis of ion-pair extraction, RP-HPLC of metal complexes, and ion chromatography of anions on an ODS column coated with Cu(II) complexes of the long alkyl derivatives. Both ion-pair extraction and HPLC studies demonstrated that a dicationic complex with 8-(3,5-dibromo-2-pyridylazo)-5-aminoquinoline interacted with anions stronger than a monocationic complex with 2-(2-pyridylazo)methylphenol. Anions were more retained on the column coated with dicationic Cu(II) complex. Such differences were quantitatively ascribed to the first ion-pair formation of the dicationic complex giving a monocationic species.     

Trypanocidal constituents in plants 6. 1) Minor withanolides from the aerial parts of Physalis angulata

Further study of the methanol extract of the aerial parts of Physalis angulata (Solanaceae) resulted in the isolation of new withanolides, designated physagulins L, M and N, together with known withanolide, physagulin D and flavonol glycoside, quercetin 3-O-rhamnosyl-(1-->6)-galactoside. The chemical structures of these new withanolides were elucidated by detailed spectroscopic analyses to be (20R,22R)-15alpha-acetoxy-5alpha,6beta,14beta,17beta,27-pentahydroxy-1-oxo-witha-2, 24-dienolide, (20S,22S)-15alpha-acetoxy-5alpha,6beta,14alpha,23beta-tetrahydroxy-1-oxo-witha-2,16,24-trienolide and (20S,22R)-15alpha-acetoxy-5beta,6beta-epoxy-14alpha-hydoxy-3beta-methoxy-1-oxo-witha-16,24-dienolide, respectively. All these compounds showed weak trypanocidal activity against trypomastigotes, an infectious form of Trypanosoma cruzi, the etiologic agent for Chagas' disease. Withanolides obtained in the previous paper showed considerable trypanocidal activity, suggesting the structure-activity relationships.     

A conventional route for the synthesis of new oxazolidin-2-one derivatives with beta-aminoalanines

A conventional new route to the novel oxazolidin-2-one derivatives (3a-f) having two substituents on N-3 and C-4 in the oxazolidin-2-one ring was established with racemic beta-aminoalanine derivatives (1) as the key starting materials.     

Pyrolysis of azidopyrazines

2,3-Dichloro- and 2,5-dichloropyrazines were treated with sodium azide. The former gave diazidopyrazines and the latter, monoazidomonochloropyrazines. Pyrolysis of 2,3-diazidopyrazines resulted the production of 1,2-dicyanoiminoethanes and that of 2-azido-5-chloropyrazines, chloroimidazoles.     

Droplet Growth Dynamics in a Water/Oil/Surfactant System

We have studied the droplet growth dynamics in a water-oil-surfactant system, using the cell dynamics system simulations based on the time-dependent Ginzburg-Landau model with two order parameters. Our simulations are carried out in a two-dimensional system of uneven composition of water and oil. For various average surfactant concentrations, the spatial patterns and their time evolution are obtained. The Ostwald ripening behaviors in the sparse regime of the droplet distributions are obtained. Numerical simulations are also extended to the dense regime so that the interactions between the droplet domains cannot be neglected. In such a system, the dynamics of pattern formation become significantly slow as the average surfactant concentration increases and we cannot apply the familiar scaling law in this case. Copyright 2001 Academic Press.     

Glycosylated tris-bipyridine ferrous complexes for probing a mechanism behind carbohydrate-carbohydrate interactions: Spatial carbohydrate packing of glycoclusters changes on additions of salts in carbohydrate- and anion-dependent manners

2,2′-Bipyridines containing two β-maltoside, β-lactoside, or β-isomaltoside appendages were prepared and successively complexed with ferrous ion to afford hexavalent glycoclusters having tris-bipyridine ferrous complex cores. Each of these metalloglycoclusters showed unique UV–vis and CD spectral changes upon addition of chloride, nitrate, and sulfate salts in carbohydrate- and anion-dependent manners. The results indicate that spatial carbohydrate packing of the metalloglycoclusters changes upon addition of these anions and that different anions stabilize different carbohydrate packings. Furthermore, the sulfates specifically enhance the rheological properties of aqueous solutions containing the metalloglycocluster containing β-lactoside appendages.     

A conventional new procedure for N-acylation of unprotected amino acids

The preparation of amide derivatives (4) by N-acylation of unprotected alpha-amino acids is easily achieved via readily available benzotriazolyl carboxylates (2a-d) or succinimidyl carboxylates (2e-f). These intermediates (2) are prepared from reaction of carboxylic acids (1) with 1-hydroxybenzotriazole (HO-Bt) or N-hydroxysuccinimide (HO-Su) in the presence of equimolar amounts of 1-ethyl-3-(3'-dimethylaminopropyl)carbodiimide hydrochloride (WSCI). The overall yields of the target compounds (4) were excellent, and this two-stage procedure could be applicable as an alternative procedure for one-pot reaction.