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Ringöffnungen von 1,2‐Didehydroprolinen, I Darstellung von 4‐Hydroxyornithin und geschützten 4‐Amino‐3‐hydroxybutyronitrilen
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Titel: |
Ringöffnungen von 1,2‐Didehydroprolinen, I Darstellung von 4‐Hydroxyornithin und geschützten 4‐Amino‐3‐hydroxybutyronitrilen |
In: | Liebigs Annalen der Chemie, 1992, 1992, 12, S. 1231-1237 |
veröffentlicht: |
Wiley
|
Umfang: | 1231-1237 |
ISSN: |
0170-2041 |
DOI: | 10.1002/jlac.1992199201205 |
Zusammenfassung: | <jats:p><jats:bold>Ring‐Opening Reactions of 1,2‐Didehydroprolines, I. — Synthesis of 4‐Hydroxyornithine and Protected 4‐Amino‐3‐hydroxybutyronitriles</jats:bold></jats:p><jats:p>The cyclic azomethines <jats:bold>6a</jats:bold>, <jats:bold>b</jats:bold>, <jats:bold>d</jats:bold> and <jats:bold>f</jats:bold> easily undergo ringopening reaction with hydroxylamine and its <jats:italic>O</jats:italic>‐alkyl derivatives leading to the oximino compounds <jats:bold>3a</jats:bold>, <jats:bold>b</jats:bold>, <jats:bold>d</jats:bold> and <jats:bold>f</jats:bold>–<jats:bold>i</jats:bold>. Dissolved alkali metals in amines (Birch conditions) give satisfactory yields of reduction products with a stereochemistry depending on the substitution pattern in <jats:bold>3b</jats:bold>, <jats:bold>d</jats:bold>, <jats:bold>f</jats:bold>–<jats:bold>i</jats:bold>. In case of <jats:bold>3d</jats:bold>, the (2<jats:italic>R</jats:italic>,4<jats:italic>R</jats:italic>) stereoisomer <jats:bold>9b</jats:bold> is the sole product, which can subsequently be cleaved to give <jats:bold>8b</jats:bold>. Compounds <jats:bold>3g</jats:bold>–<jats:bold>i</jats:bold> give predominantly the (2<jats:italic>S</jats:italic>,4<jats:italic>R</jats:italic>) product <jats:bold>8a</jats:bold>. Acylation under alkaline conditions decarboxylates the oximino compounds <jats:bold>3b</jats:bold> and <jats:bold>d</jats:bold> to the corresponding protected butyronitriles <jats:bold>14a</jats:bold>–<jats:bold>h</jats:bold>. Trifluoroacetic anhydride transforms <jats:bold>3b</jats:bold> into the nitrile <jats:bold>14i</jats:bold> together with the cyclization product <jats:bold>15</jats:bold>.</jats:p> |
Format: | E-Article |
Quelle: | Wiley (CrossRef) |
Sprache: | Englisch |