The diastereoselective synthesis of trans- and cis-4-hydroxypipecolic acids has been achieved with geometry-controlled nitrone cycloaddition chemistry. The cycloaddition of 3-butenol to enantiopure C-aminocarbonyl and C-alkoxycarbonyl nitrones having a definite (Z) and (E) configuration, respectively, occurs with complete regio- and exo selectivity. The acyclic (Z)-nitrone 12 affords two cycloadducts in a 1:1 ratio, which can be separated and converted into (2R,4R)- and (2S,4S)-4-hydroxypipecolic acids, respectively, in four steps. The cyclic (E)-nitrone 17 reacts with complete diastereofacial selectivity and the elaboration of its sole adduct gives the methyl ester of (2R,4S)-4-hydroxypipecolic acid, albeit in low yield.
The Synthesis of 4-Hydroxypipecolic Acids by Stereoselective Cycloaddition of Configurationally Stable Nitrones / F. M. Cordero; S. Bonollo; F. Machetti; A. Brandi. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1434-193X. - STAMPA. - 2006:(2006), pp. 3235-3241. [10.1002/ejoc.200600104]
The Synthesis of 4-Hydroxypipecolic Acids by Stereoselective Cycloaddition of Configurationally Stable Nitrones
CORDERO, FRANCA MARIA;MACHETTI, FABRIZIO;BRANDI, ALBERTO
2006
Abstract
The diastereoselective synthesis of trans- and cis-4-hydroxypipecolic acids has been achieved with geometry-controlled nitrone cycloaddition chemistry. The cycloaddition of 3-butenol to enantiopure C-aminocarbonyl and C-alkoxycarbonyl nitrones having a definite (Z) and (E) configuration, respectively, occurs with complete regio- and exo selectivity. The acyclic (Z)-nitrone 12 affords two cycloadducts in a 1:1 ratio, which can be separated and converted into (2R,4R)- and (2S,4S)-4-hydroxypipecolic acids, respectively, in four steps. The cyclic (E)-nitrone 17 reacts with complete diastereofacial selectivity and the elaboration of its sole adduct gives the methyl ester of (2R,4S)-4-hydroxypipecolic acid, albeit in low yield.File | Dimensione | Formato | |
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