scholarly journals Synthesis and Application of 1,2-Aminoalcohols with Neoisopulegol-Based Octahydrobenzofuran Core

Molecules ◽  
2019 ◽  
Vol 25 (1) ◽  
pp. 21 ◽  
Author(s):  
Fatima Zahra Bamou ◽  
Tam Minh Le ◽  
Bettina Volford ◽  
András Szekeres ◽  
Zsolt Szakonyi
Keyword(s):  
Antimicrobial Activity ◽  
Secondary Amine ◽  
Ring Opening ◽  
Ring Closure ◽  
Oxirane Ring ◽  
Primary Amines ◽  
Chiral Catalysts ◽  
Ring Systems ◽  
Stereoselective Reaction ◽  
Stereoselective Epoxidation

A library of 1,2-aminoalcohol derivatives with a neoisopulegol-based octahydrobenzofuran core was developed and applied as chiral catalysts in the addition of diethylzinc to benzaldehyde. The allylic chlorination of (+)-neoisopulegol, derived from natural (–)-isopulegol followed by cyclization, gave the key methyleneoctahydrobenzofuran intermediate. The stereoselective epoxidation of the key intermediate and subsequent oxirane ring opening with primary amines afforded the required 1,2-aminoalcohols. The ring closure of the secondary amine analogues with formaldehyde provided spiro-oxazolidine ring systems. The dihydroxylation of the methylenetetrahydrofuran moiety with OsO4/NMO (4-methylmorpholine N-oxide) resulted in the formation of a neoisopulegol-based diol in a highly stereoselective reaction. The antimicrobial activity of both the aminoalcohol derivatives and the diol was also explored.

scholarly journals Stereoselective Synthesis and Investigation of Isopulegol-Based Chiral Ligands

2019 ◽  
Vol 20 (16) ◽  
pp. 4050 ◽  
Author(s):  
Tam Minh Le ◽  
Tamás Szilasi ◽  
Bettina Volford ◽  
András Szekeres ◽  
Ferenc Fülöp ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Ring Opening ◽  
Stereoselective Synthesis ◽  
Substituent Effects ◽  
Ring Closure ◽  
Chiral Ligands ◽  
Primary Amines ◽  
Structure Activity ◽  
Stereoselective Reactions ◽  
Stereoselective Epoxidation

A library of isopulegol-based bi-, tri- and tetrafunctional chiral ligands has been developed from commercially available (−)-isopulegol and applied as chiral catalysts in the addition of diethylzinc to benzaldehyde. Michael addition of primary amines towards α-methylene-γ-butyrolactone, followed by reduction, was accomplished to provide aminodiols in highly stereoselective transformations. Stereoselective epoxidation of (+)-neoisopulegol, derived from natural (−)-isopulegol, and subsequent oxirane ring opening with primary amines afforded aminodiols. The regioselective ring closure of N-substituted aminodiols with formaldehyde was also investigated. Hydroxylation of (+)-neoisopulegol resulted in diol, which was then transformed into aminotriols by aminolysis of its epoxides. Dihydroxylation of (+)-neoisopulegol or derivatives with OsO4/NMO gave neoisopulegol-based di-, tri- and tetraols in highly stereoselective reactions. The antimicrobial activity of aminodiol and aminotriol derivatives as well as di-, tri- and tetraols was also explored. In addition, structure–activity relationships were examined by assessing substituent effects on the aminodiol and aminotriol systems.

scholarly journals Synthesis and Investigation of Pinane-Based Chiral Tridentate Ligands in the Asymmetric Addition of Diethylzinc to Aldehydes

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 474
Author(s):  
Mounir Raji ◽  
Tam Minh Le ◽  
Ferenc Fülöp ◽  
Zsolt Szakonyi
Keyword(s):  
Molecular Modeling ◽  
Ring Opening ◽  
Benzyl Bromide ◽  
Allylic Alcohol ◽  
Ring Closure ◽  
Reaction Pathways ◽  
Secondary Amines ◽  
Tridentate Ligands ◽  
Stereoselective Epoxidation ◽  
Carbonyl Function

A library of pinane-based chiral aminodiols, derived from natural (−)-β-pinene, were prepared and applied as chiral catalysts in the addition of diethylzinc to aldehydes. (−)-β-Pinene was reacted to provide 3-methylenenopinone, followed by a reduction of the carbonyl function to give a key allylic alcohol intermediate. Stereoselective epoxidation of the latter and subsequent ring opening of the resulting oxirane with primary and secondary amines afforded aminodiols. The regioselectivity of the ring closure of the N-substituted secondary aminodiols with formaldehyde was examined and exclusive formation of oxazolidines was observed. Treatment of the allylic alcohol with benzyl bromide provided the corresponding O-benzyl derivative, which was transformed into O-benzyl aminodiols by aminolysis. Ring closure of the N-isopropyl aminodiol derivative with formaldehyde resulted in spirooxazolidine. The obtained potential catalysts were applied in the reaction of both aromatic and aliphatic aldehydes to diethylzinc providing moderate to good enantioselectivities (up to 87% ee). Through the use of molecular modeling at an ab initio level, this phenomenon was interpreted in terms of competing reaction pathways. Molecular modeling at the RHF/LANL2DZ level of theory was successfully applied for interpretation of the stereochemical outcome of the reactions leading to display excellent (R) enantioselectivity in the examined transformation.

An analysis of the factors contributing to the regioselectivity observed in the opening of oxiranes

1980 ◽  
Vol 58 (3) ◽  
pp. 302-306 ◽  
Author(s):  
Margaret M. Kayser ◽  
Peter Morand
Keyword(s):  
Oxygen Atom ◽  
Ring Opening ◽  
Oxirane Ring ◽  
Epoxide Ring ◽  
Acid Base ◽  
Epoxide Ring Opening ◽  
Soft Acid ◽  
Hsab Theory

The regioselectivity of epoxide ring opening can be analyzed in terms of hard–soft acid–base (HSAB) theory. The coordination of the hard acid with the oxygen atom of the oxirane ring produces a "pulling effect" which determines the direction of the ring opening. In the absence of a strong "pulling effect" the "pushing effect" of the approaching base is examined and the consequences of relative softness or hardness of the nucleophile on the regioselectivity of the ring opening are discussed.

First Total Synthesis of a Fluorinated Calystegin

2010 ◽  
Vol 65 (4) ◽  
pp. 445-451 ◽  
Author(s):  
René Csuk ◽  
Erik Prell ◽  
Stefan Reißmann ◽  
Claudia Korb
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Competitive Inhibitor ◽  
Ring Closure ◽  
Target Compound ◽  
Metathesis Reaction ◽  
Grubbs Catalyst ◽  
Ring Opening Reaction ◽  
Ultrasound Assisted ◽  
Key Steps

A straightforward chiral pool synthesis for the first fluorinated calystegin is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. The target compound is a selective and competitive inhibitor for a β -glycosidase.

Are amines basic or nucleophilic catalysts for oxirane ring opening by proton-donating nucleophiles?

2016 ◽  
Vol 57 (1) ◽  
pp. 47-51 ◽  
Author(s):  
S. G. Bakhtin ◽  
E. N. Shved ◽  
Yu. N. Bespal’ko
Keyword(s):  
Ring Opening ◽  
Oxirane Ring ◽  
Nucleophilic Catalysts

ChemInform Abstract: Synthesis of Functionalized Cyclophanes by Ring-Opening/Ring-Closure Cascade Reactions of Siloxycyclopropanes.

ChemInform ◽  
2010 ◽  
Vol 30 (21) ◽  
pp. no-no
Author(s):  
Astrid Ullmann ◽  
Margit Gruner ◽  
Hans-Ulrich Reissig
Keyword(s):  
Ring Opening ◽  
Cascade Reactions ◽  
Ring Closure

Antimicrobial Activity of Novel Tetra- and Penta-azaheterocyclic Ring Systems

2016 ◽  
Vol 54 (1) ◽  
pp. 610-617
Author(s):  
Sobhi M. Gomha ◽  
Eman M. H. Abbas ◽  
Thoraya A. Farghaly
Keyword(s):  
Antimicrobial Activity ◽  
Ring Systems
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