Soon Bang Kang

A facile synthesis of N-carbamoylmethyl- α -aminobutyrolactones by the Ugi multicomponent condensation reaction

Abstract A new method of various N-carbamoylmethyl-α-amino-butyrolactones4 utilizing the intramolecular Ugi five-center-three-component condensation reaction starting from l -homoserine was developed.

Indium mediated pinacol coupling reaction of aromatic aldehydes in aqueous media

Abstract The carbon-carbon bond formation reaction of aromatic carbonyl compounds was performed with indium in neutral aqueous media using sonication affording the corresponding diols in moderate to good yields.

α-Fluorovinyl Weinreb Amides and α- Fluoroenones from a Common Fluorinated Building Block

Synthesis and reactivity of N-methoxy-N-methyl-(1,3-benzothiazol-2-ylsulfonyl)fluoroacetamide, a building block for Julia olefination, is reported. This reagent undergoes condensation reactions with aldehydes and cyclic ketones to give alpha-fluorovinyl Weinreb amides. Olefination reactions proceed under mild, DBU-mediated conditions, or in the presence of NaH. DBU-mediated condensations proceed with either E- or Z-selectivity, depending upon reaction conditions, whereas NaH-mediated reactions are > or = 98% Z-stereoselective. Conversion of the Weinreb amide moiety in N-methoxy-N-methyl-(1,3-benzothiazol-2-ylsulfanyl)fluoroacetamide to ketones, followed by oxidation, resulted in another set of olefination reagents, namely (1,3-benzothiazol-2-ylsulfonyl)fluoromethyl phenyl and propyl ketones. In the presence of DBU, these compounds react with aldehydes tested to give alpha-fluoroenones with high Z-selectivity. The use of N-methoxy-N-methyl-(1,3-benzothiazol-2-ylsulfanyl)fluoroacetamide as a common fluorinated intermediate in the synthesis of alpha-fluorovinyl Weinreb amides and alpha-fluoroenones has been demonstrated. Application of the Weinreb amide to alpha-fluoro allyl amine synthesis is also shown.

A FACILE SYNTHESIS OF (S)-(-)-7,8-DIFLUORO-3,4-DIHYDRO-3-METHYL-2H-1,4-BENZOXAZINE BY ZINC CHLORIDE ASSISTED MITSUNOBU CYCLIZATION REACTION

A convenient procedure for preparation of the title compound of ≥99% ee starting from 1-(2,3-difluoro-6-nitrophenoxy)-2-propanone (3) is presented. The key reaction is the intramolecular cyclization reaction in the presence of zinc chloride.

An efficient synthesis of 2,5-diketopiperazine derivatives by the Ugi four-center three-component reaction

A facile synthetic approach to 2,5-diketopiperazines 4 by the Ugi four-center three-component reaction using commercially available dipeptides as a bifunctional component, aldehydes, and isocyanides was described.

Indium-mediated monoallylation of carbonyl compounds with allylic chlorides and bisallylation of 2-pyridyl carboxylates with allylic halides in aqueous media

Abstract Allylic chlorides are efficient reagents in the indium-mediated Barbier-type allylation reaction with various aldehydes and ketones in pure water under sonication or in a 1:1 mixture of H 2 O and t-BuOH. Also indium is effective in bisallylation reactions of the 2-pyridyl esters with allyl halides in pure water.

A new direct allylation of the aromatic compounds with allylic chlorides catalyzed by indium metal

Abstract A new method of the direct allylation reaction for the aromatic compounds with allylic chlorides using a catalytic amount of indium in the presence of CaCO 3 4 A molecular sieves was developed.

A facile synthesis of 7-amino-3-desacetoxycephalosporanic acid derivatives by indium-mediated reduction of 3-iodomethylcephems in aqueous media

Abstract An efficient reductive conversion of 3-iodomethylcephalosporin and 3-acetoxymethylcephalosporin derivatives mediated by indium into the corresponding 3-methylcephems and 3-methylenecephams in moderate to good yields has been developed in an aqueous system. 3-Methylenecephams are converted into the corresponding 3-methylcephems under previously reported basic conditions quantitatively.

Quantitative structure activity relationship (QSAR) study of estrogen derivatives based on descriptors of energy and softness.

Quantum chemical interaction of estrogen derivatives with their receptor has been explored by using Klopman atomic softness. Four series of estrogen derivatives were taken from the literature and the structure of receptor (PDB code 1QKT) was obtained from the protein databank. It is proposed that three Lys, a His, a Tyr and a Cys residues are important for binding. The basic softness values (Em‡) and acidic softness values (En‡) of all atoms of estrogen derivatives were evaluated. The required parameters for Klopman equation were taken from PM3 results. The highest En‡ values for each molecules and highest Em‡ value for each residue were identified and ΔEnm‡ has been derived using them. The lowest ΔEnm‡ values were used in addition to Qmin (highest negative charge), ΔHf0 (heat of formation), ET (total energy), and EE (electronic energy). Multiple linear regression analysis was employed to correlate the variation of relative binding affinity values. The analyses show that ΔEnm‡ values in combination with other descriptors provide significant correlation with relative binding affinity values. The result underscores that carbonyl oxygen of the receptor is important for interaction with estrogen derivatives. This model could be utilized to predict the binding affinity of a new compound of this series.

Research Article: Quantitative Structure Activity Relationship (QSAR) Study of Estrogen Derivatives Based on Descriptors of Energy and Softness

Quantum chemical interaction of estrogen derivatives with their receptor has been explored by using Klopman atomic softness. Four series of estrogen derivatives were taken from the literature and the structure of receptor (PDB code 1QKT) was obtained from the protein databank. It is proposed that three Lys, a His, a Tyr and a Cys residues are important for binding. The basic softness values (Em‡) and acidic softness values (En‡) of all atoms of estrogen derivatives were evaluated. The required parameters for Klopman equation were taken from PM3 results. The highest En‡ values for each molecules and highest Em‡ value for each residue were identified and ΔEnm‡ has been derived using them. The lowest ΔEnm‡ values were used in addition to Qmin (highest negative charge), ΔHf0 (heat of formation), ET (total energy), and EE (electronic energy). Multiple linear regression analysis was employed to correlate the variation of relative binding affinity values. The analyses show that ΔEnm‡ values in combination with other descriptors provide significant correlation with relative binding affinity values. The result underscores that carbonyl oxygen of the receptor is important for interaction with estrogen derivatives. This model could be utilized to predict the binding affinity of a new compound of this series.