The PAUSON-KHAND REACTION IN SYNTHESIS OF BICYCLIC RIGID Α-Amino ACIDS

Wang, Jing; Falck-Pedersen, Mette Lene; Rømming, Christian; Undheim, Kjell

doi:10.1081/scc-100103996

Cited by 8 publications

(1 citation statement)

References 18 publications

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“…Hydrolysis of the separated isomers 208a and 208b under mild acidic conditions gives the highly novel α-amino acid esters 209 and 210. 56…”

Section: Scheme 46mentioning

confidence: 99%

Stereoselective Reactions in Preparation of Chiral α-Heteraspiro[m.n]alkanes

Undheim

2015

Synthesis

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The biological importance and wide occurrence of spirane systems in nature have stimulated studies in spirane chemistry. The fundamental spirane framework consists of two monocyclic rings linked in an orthogonal relationship by a common ring carbon. This review covers families of annular α-monoheteraspiranes starting with α-heteraspiro[2.4]heptanes and terminating with α-hetera[5.6]dodecanes; the annular heteroatoms are N, O, or S. The spirane systems are arranged according to the relative size of the two monocyclic rings with highest priority for the smaller ring, Often optically active spiranes are prepared for biological reasons by chemical modifications of natural products related to the spirane to be prepared. Chiral auxiliaries are useful in the introduction and control of stereochemistry in the construction of spiranes as intermediates in the preparation of novel amino acids and nucleosides. Another aspect of chiral spirane chemistry concerns modifications and conformational restrictions introduced in natural carbohydrates, nucleosides, and amino acids. 1 Introduction 2 Heteraspira[2.m]alkanes 3 Heteraspira[3.m]alkanes 4 Heteraspira[4.m]alkanes 5 Heteraspira[5.m]alkanes Key words α-heteraspiranes, chirons, stereoselective syntheses, spiroannulations, spirocyclic amino acids, spirocyclic nucleosides 2 Heteraspiro[2.m]alkanes 2.1 Heteraspiro[2.4]heptanes 2.1.1 4,6-Diazaspiro[2.4]heptane The Seebach chiron, tert-butyl (2S)-2-tert-butyl-3methyl-4-oxoimidazoline-1-carboxylate, was developed for the stereoselective construction of α-amino acids. 11 The chiron has also been used for the stereoselective synthesis of cyclic amino acids via a spirane. During lithiation of tertbutyl (2S)-2-tert-butyl-3-methyl-4-oxoimidazoline-1-carboxylate at the 5-position, the tert-butyl substituent effectively shields one face of the ylide from electrophilic attack. Thus acetate 1 (Scheme 1) is available from lithiated Seebach chiron and methyl α-bromoacetate. In a synthesis of 1-amino-2,2-dideuteriocyclopropane-1-carboxylic acid (4) via spirane 3, substrate 1 is stepwise lithiated by lithium

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“…Hydrolysis of the separated isomers 208a and 208b under mild acidic conditions gives the highly novel α-amino acid esters 209 and 210. 56…”

Section: Scheme 46mentioning

confidence: 99%