Stereoselective Synthesis of (Z)‐ and (E)‐Allyl Aryl Sulfides and Selenides from Baylis?Hillman Acetates under Neutral Conditions Using β‐Cyclodextrin in Water

The first example of the stereoselective synthesis of (Z)‐ and (E)‐allyl aryl sulfides and selenides from Baylis? Hillman acetates under neutral conditions in H₂O by supramolecular catalysis involving β‐cyclodextrin is reported. β‐Cyclodextrin can be recovered and reused. The reaction is very efficient in providing allyl aryl sulfides and selenides in good‐to‐excellent yields with clean reaction profiles under mild reaction conditions.     

Synthesis of N-substituted-2-aminobenzothiazoles using nano copper oxide as a recyclable catalyst under ligand-free conditions in reusable PEG-400 medium

A simple and practical method for the synthesis of N-substituted-2-aminobenzothiazoles via a crosscoupling reaction of 2-iodo anilines with isothiocyanates is envisaged using nano copper oxide as a recyclable catalyst and Cs2CO3as a base in PEG-400,as a bio-degradable,reusable,inexpensive and nontoxic reaction medium,under ligand-free conditions.The present tandem process underlines environmental acceptability to access a wide range of N-substituted-2-aminobenzothiazoles in good to excellent yields.     

Obtaining functional form for chaotic time series evolution using genetic algorithm

A genetic algorithm (GA) based strategy is presented for deducing an exact or near-exact functional form from a time series. The GA formalism proposed here utilizes (i) the "postfix" representation with a view to reduce the procedural complexities and (ii) the "elitist mating" scheme to produce fitter offspring strings. The GA procedure is exemplified by considering chaotic time series of the well-known logistic, Henon and universal maps. The GA correctly recovers the underlying functional forms for the respective time series. Measurements from a number of finite-dimensional physical, biological, and other systems often give rise to complex time series and the presented methodology should prove useful in obtaining functional forms describing accurately the evolution of the time series. (c) 1999 American Institute of Physics.     

Recyclable heterogeneous copper oxide on alumina catalyzed coupling of phenols and alcohols with aryl halides under ligand-free conditions

An efficient alumina-supported CuO-catalyzed O-arylation of phenols and aliphatic alcohols with various aryl as well as heteroaryl halides under ligand-free conditions are reported. This protocol provides a variety of diaryl ether and bis-diaryl ether motifs by reacting different aryl/aliphatic halides with differently substituted phenols and saturated alcohols in the presence of a catalytic amount of CuO on alumina and KOH as a base at moderate temperature under nitrogen atmosphere. The described methodology is simple, straightforward and efficient to afford the cross-coupled products in high yields under ligand-free conditions. The explored catalyst is inexpensive, air-stable and recyclable up to three cycles.     

Synthesis of Allyl Aryl Sulfone Derivatives from Baylis?Hillman Acetates in Water

Various phenyl and p‐tolyl allyl sulfone derivatives were prepared stereoselectively by reacting Baylis? Hillman acetates with sodium 4‐R‐benzenesulfinate (R=H, Me) in H₂O. The reaction was very efficient in providing the corresponding sulfone derivatives in good to excellent yields (Table).     

Synthetic Heparanase Inhibitors Can Prevent Herpes Simplex Viral Spread

Herpes simplex virus (HSV-1) employs heparan sulfate (HS) as receptor for cell attachment and entry. During late-stage infection, the virus induces the upregulation of human heparanase (Hpse) to remove cell surface HS allowing viral spread. We hypothesized that inhibition of Hpse will prevent viral release thereby representing a new therapeutic strategy for HSV-1. A range of HS-oligosaccharides was prepared to examine the importance of chain length and 2-O-sulfation of iduronic moieties for Hpse inhibition. It was found that hexa- and octasaccharides potently inhibited the enzyme and that 2-O-sulfation of iduronic acid is tolerated. Computational studies provided a rationale for the observed structure–activity relationship. Treatment of human corneal epithelial cells (HCEs) infected with HSV-1 with the hexa- and octasaccharide blocked viral induced shedding of HS which significantly reduced spread of virions. The compounds also inhibited migration and proliferation of immortalized HCEs thereby providing additional therapeutic properties.     

Modified Cyclodextrins as Enantioselective Hosts for Amino Acids

Two modified β‐cyclodextrins, H‐2 and H‐3 , having a flexible appended moiety were studied for the chiral discrimination of the enantiomers of various amino acids by means of fluorescence as signaling option. These hosts quenched the fluorescence intensities of amino acids upon binding. The d‐ enantiomers were better recognized by these hosts. The association constants (K_s) and enantioselectivity factors (α) of the host?guest complexes were calculated.     

Functionalized self-assembled monolayers on ultraflat gold as platforms for single molecule force spectroscopy and imaging

Single molecule force spectroscopy is a valuable tool for studying unfolding and nanomechanical properties of proteins. The common practice is to stretch proteins from a surface that was dosed to give a reasonable hit rate and to analyze the curves that exhibit the expected characteristics of a single polymer. Whether the surface-bound proteins are indeed single and isolated remains unclear, and the undesirable protein/surface interactions that obscure informative features of the force curves are implicitly assumed to be absent. In this study, mixed self-assembled monolayers (SAMs) consisting of N-hydroxysuccinimide (NHS) and oligoethylene glycol (OEG) terminated thiols on an ultraflat gold surface were used to covalently immobilize proteins via lysine residues. By the optimization of attachment sites via lysine-NHS linkages amidst a protein-resistant layer of the OEG SAM, it was possible to isolate single proteins for study in a controlled fashion. The single protein distribution on the surface is clearly demonstrated by atomic force microscopy (AFM) imaging. The OEG also significantly reduces nonspecific tip-surface interactions between the cantilever and surface. Stretching covalently attached single proteins produces high-quality and reproducible force-extension curves. This experimental strategy is an attractive platform with which to study protein structure, interactions, and nanomechanical properties of single proteins.     

Chiral Recognition of Zolmitriptan by Modified Cyclodextrins

The two pyrrolidinylidenesulfamido‐modified β‐cyclodextrins (β‐CDs) 3 and 4 were prepared and studied for chiral discrimination of the enantiomers (R)‐ and (S)‐ 1 of zolmitriptan. The pyrrolidinylidenesulfamido spacer improved the chiral discrimination and binding abilities of these modified cyclodextrins. The hosts 3 and 4 showed higher selectivity for (S)‐ 1 . The association constants (Table) and enantioselectivity factors were calculated for the complexes of (R)‐ and (S)‐ 1 with the β‐CDs 2 – 4 . The formation of host?guest complexes was confirmed by ¹H‐NMR studies.