Highly Enantioselective Hydrogenation of β‐Alkyl and β‐(ω‐Chloroalkyl) Substituted β‐Keto Esters

Highly enantioselective hydrogenation of β‐alkyl and β‐(ω‐chloroalkyl) substituted β‐keto esters was achieved with Ru catalysts based on chiral diphosphines in EtOH at 50°C under 50‐bar initial hydrogen pressure, affording the corresponding β‐hydroxy esters in >98% ee.     

Conversion of Epoxides to β‐Chlorohydrins with Thionyl Chloride and β‐Cyclodextrin in Water

Several epoxides are efficiently converted to the corresponding β‐chlorohydrins in impressive yields with thionyl chloride in the presence of β‐cyclodextrin using water as solvent at room temperature.     

Synthesis of Monocyclic β‐Lactams via Cyclodehydration of β‐Amino Acids Using POCl3

Abstract

β‐Lactams 2 have been synthesized through a convenient use of POCl₃ via cyclodehydration of β‐amino acids 1.     

Efficient Synthesis of β‐Primeverosides as Aroma Precursors by Transglycosylation of β‐Diglycosidase from Penicillium multicolor

The enzyme activity transferring a β‐primeverosyl unit was found from culture filtrates of Penicillium multicolor IAM7153 and was useful for synthesizing a series of β‐primeverosides via a β‐primeverosyl transfer reaction in an aqueous‐organic biphasic system. With the acceptors benzyl alcohol, 2‐phenylethanol, and (Z)‐3‐hexenol, the enzyme induced the transfer products benzyl, 2‐phenylethyl, and (Z)‐3‐hexyl β‐primeverosides in high yields of 51% to 70% based on the donor added. When geraniol and eugenol were used as acceptors, the corresponding geranyl and eugenyl β‐primeverosides were obtained in lower yields of 8% to 12%. The enzyme was an excellent tool for producing naturally occurring β‐primeverosides on a mmol scale.     

Synthesis of 3,6‐Branched β‐d‐Glucose Oligosaccharides

A glucohexasaccharide, β‐d‐Glcp‐(1 → 3)‐[β‐d‐Glcp‐(1 → 3)‐β‐d‐Glcp‐(1 → 6)]‐β‐d‐Glcp‐(1 → 3)‐β‐d‐Glcp‐(1 → 3)‐β‐d‐Glcp was synthesized as its 4‐methoxyphenyl glycoside via 2 + 2 + 2 strategy with benzylidenated glucose mono‐ and disaccharides as the key intermediates.     

Spectrophotometric Study of the Interaction of β‐Cyclodextrin with Hydroxamic acids

Cyclodextrins have attracted considerable interest because of their ability to form stable inclusion complexes with a wide variety of inorganic and organic guest molecules. In the present communication, binding constant of β‐cyclodextrin and a series of substituted benzohydroxamic acids (X‐C₆H₄CON(OH)H), X=H, 4‐NO₂, 4‐Me 4‐OMe, and 2‐OH and N‐phenylbenzohydroxamic acid (C₆H₅CON(OH)C₆H₅) were determined at 27°C spectrophotometrically. In all the cases the formation of 1:1 host‐guest complex was established. The addition of β‐CD results in an increase in the absorbance intensity but does not cause a shift in λ_max. The values of binding constants are in good agreement with in those determined from kinetic and pH metric techniques.     

Selective Synthesis of β‐Hydroxy Nitroethanol Ethers by Alcoholysis of Oxiranes

β‐Hydroxy nitroethanol ethers are prepared by selective alcoholysis of oxiranes. The best results are obtained using a clay (monmorillonite K10) or a π‐acid (TCNE) as the catalyst.     

Asymmetric Synthesis of β‐DDB Through Oxazoline‐Mediated Ullmann Coupling

Biphenyl lignan (β‐DDB) (2), an effective drug in the treatment of hepatitis, was for the first time asymmetrically synthesized via a chiral oxazoline mediated Ullmann coupling. The two enantiomers of β‐DDB have been obtained in this way by using the optically pure amino alcohols L‐valinol and D‐valinol, respectively. However, attempts to synthesize enantiopure α‐DDB (1) by the same method failed because of the racemization of 1 at room temperature in solution.     

Novel and Efficient Approach to Fluorinated β‐Aminobutanones Catalyzed by Molecular Iodine

A variety of fluorinated compounds of β‐amino ketones could be obtained in good to excellent yields at room temperature through a three‐component Mannich reaction of aldehydes, anilines, and acetones catalyzed by iodine.     

Synthesis of Nitrogen Heterocycles from Methyl α‐ and β‐d‐Glucopyranosides

Eight nitrogen heterocycles, mono and disubstituted tetrazoles and oxadiazoles, were synthesized from methyl d‐glucopyranoside anomers. The monosubstituted tetrazoles resulted from the reaction of 6‐cyanoglucopyranoside derivatives with sodium azide. By alkylation of the monosubstituted tetrazoles, the 1,5 and 2,5 disubstituted tetrazoles were obtained. The monosubstituted tetrazoles were reacted with acetic anhydride to give the oxadiazoles.     

Synthesis of Novel Caged Intramolecular Ketals of β‐C‐Glycopyranosidic Ketones

Novel caged intramolecular ketals of β‐C‐glycosidic ketones were prepared from pyranoses. The structures of the new compounds were elucidated by NMR and HRMS spectral analysis. Preliminary studies revealed that the intramolecular ketal could be used to protect 3‐ and 6‐hydroxyl groups of β‐C‐glycosidic ketones.     

Facile Synthesis of Isoquinolines, β‐Carbolines,and 3‐Deazapurines

Isoquinoline, β‐carbolines, and 3‐deazapurines were prepared in 52–81% yields via oxidative decarboxylation of cyclic α‐amino acids using ammonium persulfate as an oxidant in the presence of catalytic silver.     

Facile and Efficient Synthesis of Substituted 1,4‐Dithiafulvalenes from β‐Dicarbonyl Compounds

A facile and efficient synthetic route to substituted 1,4‐dithiafulvalenes has been developed. The precursors 2 may be easily prepared from the reactions of β‐dicarbonyl compounds 1 with CS₂ and 1,2,3‐tribromopropane under mild conditions. The elimination of HBr of 2 in basic media furnishes corresponding acetyl substituted 1,4‐dithiafulvalenes 3 in 85–93% yields. The aldol condensation reaction of 2 with various arylaldehydes affords alkenoyl substituted 1,4‐dithiofulvalenes 4 in high to excellent yields.     

Inclusion Compounds Formation of Poly(azomethine ether)s and β‐Cyclodextrin

In this study, two poly(azomethine ether)s were synthesized and they can form inclusion compounds (ICs) with β‐cyclodextrin (β‐CD). Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance spectroscopy (¹H‐NMR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD) have been utilized to observe the formation of polymer‐CD‐ICs. The differentiation in their FTIR spectra may indicate the formation of the inclusion compounds between poly(azomethine ether)s and β‐CD. Compared the ¹H‐NMR of polymer‐CD‐ICs with β‐CD, proton signals belonging to both β‐CD and poly(azomethine ether)s can be found in the spectrum. The chemical shift of the protons H‐3, H‐5 has changed after the formation of inclusion compounds, which is perhaps due to the interaction of these protons with polymers. TGA scans showed the much higher decomposition temperatures observed for two polymer‐CD‐ICs may imply that polymer chains included inside the β‐CD's cavity can greatly improve β‐CD's stabilities. The X‐ray diffraction patterns were confirmed to be the new crystal structures.     

Deprotection of Oximes using Iodosobenzene in the Presence of β‐Cyclodextrin in Water

A mild and efficient method for the regeneration of carbonyl compounds from oximes at room temperature in impressive yields has been developed using iodosobenzene/KBr in the presence of β‐cyclodextrin in water.     

New Preparation Methods for α‐Damascone, γ‐Damascone,and β‐Damascenone using Pyronenes

γ‐ and δ‐Pyronenes are terpenic synthons easily available from myrcene. They are used as intermediates in the synthesis of α‐damascone, γ‐damascones, and β‐damascenone.     

Development of Lactose Biosensor Based on β‐Galactosidase and Glucose Oxidase Immobilized into Gelatin

In this article, we describe the preparation of a new lactose biosensor based on electrode coating with β‐galactosidase and glucose oxidase immobilized gelatin. For this purpose, β‐galactosidase and glucose oxidase enzymes were immobilized onto gelatin by crosslinking with glutaraldehyde. Properties of the immobilized β‐galactosidase and glucose oxidase enzymes electrode have been studied. The effects of glutaraldehyde concentration, temperature and pH variations and reusability were among the subjects analyzed. Lactose biosensors were subjected to continuous repeated use in order to observe reusability and shelf life; where standard lactose and milk samples were used as substrate solutions. Continuous reuse experiments showed that most of the lactose biosensors activities were retained even after the 10th use in a period of 30 days.     

Competitive Destabilization/Stabilization of β‐Lactoglobulin Foam by PEO‐PPO‐PEO Polymeric Surfactants

The effect on β‐lactoglobulin foamability and foam stability of the poly(ethylene oxide)‐poly(propylene oxide) block copolymers F127 (PEO₉₉‐PPO₆₅‐PEO₉₉), molecular weight 12500 g/mol, and P85 (PEO₂₆‐PPO₃₉‐PEO₂₆), molecular weight 4600 g/mol, has been investigated at constant protein concentration, 10 µM (0.2 mg/L), and varying block copolymer concentrations, ranging from 0.02 to 1600 µM. Foam was generated by means of air sparging and the foam volume and liquid volume of the foam were measured for one hour. It was found that foam stabilized by F127 or P85 in the concentration range 20–1600 µM contained a larger liquid volume initially than pure β‐lactoglobulin foam. Furthermore, β‐lactoglobulin foamability was only marginally affected by the presence of F127, while it was reduced in an interval of low P85 concentrations. The protein foam stability was retained in the presence of the larger polymer F127, whereas P85 largely reduced the stability, indicating that the size of the polymeric surfactant is important. The results are discussed in relation to surface rheological properties and forces acting across foam films. Steric repulsion generated between the surfaces of foam films is suggested to be the main stabilizing factor in dry foam containing F127. The instability of the mixed β‐lactoglobulin/P85 system is suggested to be caused by two effects. First, there are incompatible stabilization mechanisms of block copolymer and protein, as supported by previous surface rheological data. Second, there is a reduced importance of long‐range steric repulsion when P85 is added, compared to the case where F127 and β‐lactoglobulin are mixed.     

Reaction of β‐Lapachone with 1,2‐Diamines: Facile Synthesis of Novel Tetracyclic Pyrazines

The reactions of β‐lapachone (1) with 1,2‐diaminoethane (2) and 1,2‐diaminopropane (4) gave the tetracyclic pyrazine derivatives (3) and mixtures of (5) and (6), respectively, while reaction with o‐phenylene diamine (7) gave the quinoxaline derivative (8). The structure of pyrazine derivative (3) is confirmed by single‐crystal X‐ray diffraction study.     

Efficient Regioselective Ring Opening of Oxiranes with Thioacids in the Presence of β‐Cyclodextrin in Water

A mild and convenient synthesis of β‐hydroxy thioesters has been achieved by the regioselective ring opening of oxiranes using thioacetic acid and thiobenzoic acid in the presence of β‐cyclodextrin in water at room temperature. β‐Hydroxy thioesters are realized in high yields, and β‐cyclodextrin can also be recovered and reused.