AN ALTERNATIVE STRATEGY FOR THE PURIFICATION OF<i>meso</i>-2,4-PENTANEDIOL

Gordillo, Barbara; Hernández, Jesús

doi:10.1080/00304949709355183

Cited by 9 publications

(8 citation statements)

References 30 publications

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“…meso -2,4-Pentanediol (1). Flash chromatography (Et 2 O) of commercial dl / meso -2,4-pentanediol gave pure meso -2,4-pentanediol ( 1 ) (>99% de) as a pale yellow, highly viscous oil about to crystallize. 1 H NMR (300 MHz, CDCl 3 ) δ 4.05 (m, 2H), 3.03 (br s, 2H), 1.53 (m, 2H), 1.20 (d, J = 6.3, 6H); 13 C NMR (75 MHz, CDCl 3 ) δ 68.7, 46.1, 24.0.…”

Section: Methodsmentioning

confidence: 99%

On the Mechanism of the Unexpected Facile Formation of meso-Diacetate Products in Enzymatic Acetylation of Alkanediols

Edin

Bäckvall

2003

J. Org. Chem.

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The mechanism of the unexpected facile formation of meso-diacetate previously observed in the enzymatic resolution of dl/meso mixtures of 2,4-pentanediol and 2,5-hexanediol with Candida antarctica lipase B has been elucidated. It was found that the formation of meso-diacetate proceeds via different mechanisms for the two diols. Enzyme-catalyzed acylation of AcO-d(3) labeled (R)-monoacetates of meso-2,4-pentanediol and meso-2,5-hexanediol and analysis of the meso-diacetates obtained show that the former reaction proceeds via intramolecular acyl migration while the latter occurs via direct S-acylation of the alcohol. For the (R)-monoacetate of (R,S)-2,4-pentanediol the intramolecular acyl migration was fast and therefore direct S-acylation by the external acyl donor is suppressed. For the hexanediol monoacetate the rate ratio (pseudo E value) between (5R,2R)- and (5R,2S)-5-acetoxy-2-hexanol was experimentally determined to be k(R,R)/k(R,S) = 25, which is about 10-20 times lower than the E value for 2-pentanol and 2-octanol. In a preliminary experiment it was demonstrated that facile acyl migration in the 1,3-diol derivative can be utilized to prepare syn-1,3-diacetoxynonane (>90% syn) in high enantioselectivity (>99% ee) via a chemoenzymatic dynamic kinetic asymmetric transformation of a meso/dl mixture of 1,3-nonanediol.

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Section: Methodsmentioning

confidence: 99%

On the Mechanism of the Unexpected Facile Formation of meso-Diacetate Products in Enzymatic Acetylation of Alkanediols

Edin

Bäckvall

2003

J. Org. Chem.

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“…These compounds were prepared from meso-pentane-2,4-diol 19 by the stereospecific approach described in ref. 20.…”

Section: Cis-and Trans-aryl Thiophosphates (1-7)mentioning

confidence: 99%

The lack of influence of electronic effects on the stereochemistry of the oxidation of aryl thiophosphates

Gordillo¹,

Salas²,

Hernández³

1999

J. Chem. Soc., Perkin Trans. 2

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“…3 Alternatively, Gordillo and Hernańdez obtained syn-1 via conversion to a cyclic phosphorochloridite in low yield (23%), albeit with high selectivity (dr s/a = 99:1). 4 Recently, Nichols and co-workers prepared syn-1 by selective formation of the syn-acetal (syn-2) with acetophenone and subsequent hydrogenolysis of the acetal protecting group. 5 None of the previously reported methods are adequate to obtain both syn-1 and anti-1 in high diastereomeric purity and high yield.…”

Section: ■ Introductionmentioning

confidence: 99%

“…These useful building blocks are often produced as mixtures of syn and anti diastereomers in varying ratios, and separation of the two isomers can be challenging. For example, separation of the syn and anti diastereomers of 2,4-pentanediol ( 1 ) has been a laborious and inefficient task. − Pritchard and Vollmer reported a separation of syn - and anti -2,4-pentanediol diastereomers by formation of the cyclic sulfite ester diastereomers followed by separation via fractional distillation (a difficult operation because of their similar boiling points) and then hydrolysis . Diastereoselective formation of the syn cyclic sulfite ester could be effected in a syn / anti diastereomeric ratio (dr s / a ) of 96:4, but subsequent alkaline hydrolysis of the sulfite ester furnished syn - 1 with only moderate enrichment (dr s / a = 69:31) .…”

Section: Introductionmentioning

confidence: 99%

“…Diastereoselective formation of the syn cyclic sulfite ester could be effected in a syn / anti diastereomeric ratio (dr s / a ) of 96:4, but subsequent alkaline hydrolysis of the sulfite ester furnished syn - 1 with only moderate enrichment (dr s / a = 69:31) . Alternatively, Gordillo and Hernández obtained syn - 1 via conversion to a cyclic phosphorochloridite in low yield (23%), albeit with high selectivity (dr s / a = 99:1) . Recently, Nichols and co-workers prepared syn - 1 by selective formation of the syn -acetal ( syn - 2 ) with acetophenone and subsequent hydrogenolysis of the acetal protecting group .…”

Section: Introductionmentioning

confidence: 99%

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Efficient Separation of Diastereomeric Mixtures of syn- and anti-2,4-Pentanediol

Pan

Zhang

et al. 2015

Org. Process Res. Dev.

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A simple and practical process was developed for the efficient separation of diastereomeric syn- and anti-2,4-pentanediol by selective acetalization of a diastereomeric mixture of the 2,4-pentanediols and selective hydrolysis of the corresponding acetals. The process relies upon the reaction rate differences of syn-2,4-pentanediol (syn-diol) and anti 2,4-pentanediol (anti-diol) in acetalization and of the corresponding acetals in hydrolysis: the syn-diol reacts faster to form a more stable acetal than the anti-diol, which in turn is more susceptible to hydrolysis by Brønsted acid. Acetalization of a 2,4-pentanediol diastereomeric mixture (syn/anti = 45:55) with acetophenone (0.95 equiv relative to syn-diol) leads to the formation of a syn-enriched acetal mixture with a syn/anti diastereomeric ratio (dr s/a ) of 6:1, leaving an anti-enriched diol mixture (dr s/a = 1:7). Subsequent kinetic resolution via selective hydrolysis of the minor anti-acetal with a catalytic amount of 1.0 N HCl at ambient temperature affords the pure syn-acetal (dr s/a > 99:1) in the organic phase and the anti-enriched 2,4-pentanediols (dr s/a = 1:6) in the aqueous phase, which are conveniently separated by a phase cut. Hydrolysis of the syn-acetal is facile in alcohol solvents at elevated temperatures (60–80 °C), yielding the pure syn-diol. A second acetalization of the anti-enriched 2,4-pentanediols leads to the pure anti-2,4-pentanediol. This separation gives the syn-diol in 75–79% yield with dr s/a > 99:1 and the anti-diol in 79–85% yield with dr a/s > 98:2. Additionally, the acetophenone used for the acetalization can be recovered in 88–92% yield, and therefore, the overall process is high-yielding, atom-economical, and potentially recyclable.

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AN ALTERNATIVE STRATEGY FOR THE PURIFICATION OFmeso-2,4-PENTANEDIOL

Cited by 9 publications

References 30 publications

On the Mechanism of the Unexpected Facile Formation of meso-Diacetate Products in Enzymatic Acetylation of Alkanediols

On the Mechanism of the Unexpected Facile Formation of meso-Diacetate Products in Enzymatic Acetylation of Alkanediols

The lack of influence of electronic effects on the stereochemistry of the oxidation of aryl thiophosphates

Efficient Separation of Diastereomeric Mixtures of syn- and anti-2,4-Pentanediol

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