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Asymmetric Syntheses via Heterocyclic Intermediates, XXXIII. Asymmetric Synthesis of (Diastereomerically and Enantiomerically Virtually Pure) Methyl (2R,3S)-threo-2-Amino-3-hydroxy-4-alkenoates by the Bislactim Ether Method

✍ Scribed by Schöllkopf, Ulrich ;Bardenhagen, Jürgen

Publisher: John Wiley and Sons
Year: 1987
Tongue: English
Weight: 534 KB
Volume: 1987
Category: Article
ISSN: 0947-3440
DOI: 10.1002/jlac.198719870343

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✦ Synopsis

The titanium derivative 4a of the bislactim ether l a from cyclo-(L-Val-Gly) reacts with + m a t u r a t e d aldehydes 5 exclusively by 1.2-addition in a highly diastereowlective mode to give virtually only the (2R,l'S) diastereomers of type 6. Upon hydrolysis these furnish the methyl (2R,3S)-thrm-2-amino-3-hydroxy4dkenoates of type 11 -13 which are essentially diastereomerically and enantiomerically pure.

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## Abstract The titanium derivative 2 of the bislactim ether 1 of cyclo(‐L‐Val‐Gly‐) reacts with aldehydes and ketones 3 highly diastereoselectively to give the __syn__‐addition products 4. Upon hydrolysis with diluted trifluoroacetic acid the compounds 4 yield besides methyl L‐valinate the (2__R__