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Miguel Ramirez

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Papers by Miguel Ramirez

Research paper thumbnail of A new selective cleavage of N, N-dicarbamoyl-protected amines using lithium bromide

The Journal of Organic …, 2003

Preparation of Dimethyl (2S)-2-[(tert-Butoxy)carbonylamino]pentane-1,5-dioate (2b). To a stirred ... more Preparation of Dimethyl (2S)-2-[(tert-Butoxy)carbonylamino]pentane-1,5-dioate (2b). To a stirred solution of 2a 1 (300 mg, 0.8 mmol) in acetonitrile (9 mL) placed into a round-bottomed flask (25 mL) equipped with a stopper was added commercially available lithium bromide (210 g, 2.45 mmol). The mixture was warmed with stirring to 65 °C for 10 h, at which time the reaction was completed. The reaction mixture was concentrated and purified by silica gel chromatography to yield 2b ((216 mg, 98%)) as an oil: [α] 25 D = +11 (c 3, CHCl 3); 1 H NMR (CDCl 3) δ 1.

Research paper thumbnail of A new selective cleavage of N, N-dicarbamoyl-protected amines using lithium bromide

The Journal of Organic …, 2003

Preparation of Dimethyl (2S)-2-[(tert-Butoxy)carbonylamino]pentane-1,5-dioate (2b). To a stirred ... more Preparation of Dimethyl (2S)-2-[(tert-Butoxy)carbonylamino]pentane-1,5-dioate (2b). To a stirred solution of 2a 1 (300 mg, 0.8 mmol) in acetonitrile (9 mL) placed into a round-bottomed flask (25 mL) equipped with a stopper was added commercially available lithium bromide (210 g, 2.45 mmol). The mixture was warmed with stirring to 65 °C for 10 h, at which time the reaction was completed. The reaction mixture was concentrated and purified by silica gel chromatography to yield 2b ((216 mg, 98%)) as an oil: [α] 25 D = +11 (c 3, CHCl 3); 1 H NMR (CDCl 3) δ 1.

Research paper thumbnail of Acid-Mediated Highly Regioselective Oxidation of Substituted Furans: A Simple and Direct Entry to Substituted Butenolides

Synlett, 2005

... Juan P. Ceñal a , Carlos R. Carreras a , Carlos E. Tonn a , Juan I. Padrón b , Miguel A. Ramí... more ... Juan P. Ceñal a , Carlos R. Carreras a , Carlos E. Tonn a , Juan I. Padrón b , Miguel A. Ramírez b , David D. Díaz b , Fernando García-Tellado c , Victor S. Martín* b. ... Chem. 1987, 52: 4631. 14 Tonn CE, Gianello JC, Giordano OS,An. Asoc. Quim. Argent. 1979, 67: 1. ...

Research paper thumbnail of Stereocontrolled synthesis of 1-acetylen-2,3-di-o-benzyl-tetrahydrofurans, 1,4-anhydro-arabinitol, and α,β-dihydroxy-γ-alkyl-butyrolactones

Chirality, 2003

This article describes a concise and efficient synthesis of 1-acetylen-2,3di-O-benzyl-tetrahydrof... more This article describes a concise and efficient synthesis of 1-acetylen-2,3di-O-benzyl-tetrahydrofurans from tartaric acid esters using as the key step the stereocontrolled cyclization of Co 2 (CO) 6 -complexed propargylic diols. This molecule led to enantiomerically pure 1,4-anhydro-arabinitol and ␣,␤-dihydroxy-␥-alkyl-butyrolactones. In the latter case, the critical methylene oxidation at the oxygen vicinal position was performed by RuO 4 . Chirality 15: 148-155, 2003.

Research paper thumbnail of A new selective cleavage of N, N-dicarbamoyl-protected amines using lithium bromide

The Journal of Organic …, 2003

Preparation of Dimethyl (2S)-2-[(tert-Butoxy)carbonylamino]pentane-1,5-dioate (2b). To a stirred ... more Preparation of Dimethyl (2S)-2-[(tert-Butoxy)carbonylamino]pentane-1,5-dioate (2b). To a stirred solution of 2a 1 (300 mg, 0.8 mmol) in acetonitrile (9 mL) placed into a round-bottomed flask (25 mL) equipped with a stopper was added commercially available lithium bromide (210 g, 2.45 mmol). The mixture was warmed with stirring to 65 °C for 10 h, at which time the reaction was completed. The reaction mixture was concentrated and purified by silica gel chromatography to yield 2b ((216 mg, 98%)) as an oil: [α] 25 D = +11 (c 3, CHCl 3); 1 H NMR (CDCl 3) δ 1.

Research paper thumbnail of A new selective cleavage of N, N-dicarbamoyl-protected amines using lithium bromide

The Journal of Organic …, 2003

Preparation of Dimethyl (2S)-2-[(tert-Butoxy)carbonylamino]pentane-1,5-dioate (2b). To a stirred ... more Preparation of Dimethyl (2S)-2-[(tert-Butoxy)carbonylamino]pentane-1,5-dioate (2b). To a stirred solution of 2a 1 (300 mg, 0.8 mmol) in acetonitrile (9 mL) placed into a round-bottomed flask (25 mL) equipped with a stopper was added commercially available lithium bromide (210 g, 2.45 mmol). The mixture was warmed with stirring to 65 °C for 10 h, at which time the reaction was completed. The reaction mixture was concentrated and purified by silica gel chromatography to yield 2b ((216 mg, 98%)) as an oil: [α] 25 D = +11 (c 3, CHCl 3); 1 H NMR (CDCl 3) δ 1.

Research paper thumbnail of Acid-Mediated Highly Regioselective Oxidation of Substituted Furans: A Simple and Direct Entry to Substituted Butenolides

Synlett, 2005

... Juan P. Ceñal a , Carlos R. Carreras a , Carlos E. Tonn a , Juan I. Padrón b , Miguel A. Ramí... more ... Juan P. Ceñal a , Carlos R. Carreras a , Carlos E. Tonn a , Juan I. Padrón b , Miguel A. Ramírez b , David D. Díaz b , Fernando García-Tellado c , Victor S. Martín* b. ... Chem. 1987, 52: 4631. 14 Tonn CE, Gianello JC, Giordano OS,An. Asoc. Quim. Argent. 1979, 67: 1. ...

Research paper thumbnail of Stereocontrolled synthesis of 1-acetylen-2,3-di-o-benzyl-tetrahydrofurans, 1,4-anhydro-arabinitol, and α,β-dihydroxy-γ-alkyl-butyrolactones

Chirality, 2003

This article describes a concise and efficient synthesis of 1-acetylen-2,3di-O-benzyl-tetrahydrof... more This article describes a concise and efficient synthesis of 1-acetylen-2,3di-O-benzyl-tetrahydrofurans from tartaric acid esters using as the key step the stereocontrolled cyclization of Co 2 (CO) 6 -complexed propargylic diols. This molecule led to enantiomerically pure 1,4-anhydro-arabinitol and ␣,␤-dihydroxy-␥-alkyl-butyrolactones. In the latter case, the critical methylene oxidation at the oxygen vicinal position was performed by RuO 4 . Chirality 15: 148-155, 2003.

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