Loading...
Please wait, while we are loading the content...
Similar Documents
Asymmetric syntheses via heterocyclic intermediates. XXII: Enantioselective synthesis of α-alkenyl glycine methyl esters and α-alkenyl glycines (β-, γ-unsaturated amino acids)
| Content Provider | Semantic Scholar |
|---|---|
| Author | Schoellkopf, Ulrich Nozulak, Joachim Groth, Ulrich |
| Copyright Year | 1984 |
| Abstract | Abstract Enantioselective syntheses of α-alkenyl glycines of type 10 and of type 23 are described that provide these uncommon amino acids with predictable configuration and with ee-values of >95%. Both approaches are based on the bislactim ether method developed by Schollkopf . As for 10 : The lithiated bis-lactim ether 6 of cyclo (L-val-gly) is reacted with 2-[(dimethyl t-butyl)silyl]alkanals 2 to give the addition products 7 with de>95%. These on acid hydrolysis afford L-valinate 8 and the methyl (2 R )-2-amino-4-(dimethyl t-butyl)silyl-3-hydroxyalkanoate 9 which are convertible into the ( R )-α-alkenyl glycines of type 10 . The scope of this synthesis is limited by the fact that the compounds 9 are thermolabile when disubstitued at C-4. As for 23 : The lithiated bis-lactim ether 6 is reacted with thioketones 14 to give the addition products 15 with de>95% The S -methyl compounds 16 undergo elimination to give regioselectively the olefins 18 when treated with Raney-Ni Alternatively, the olefins 18 are obtained from the sulfonium salts 24 by dimethyl sulfide elimination, although this route is less regiospecific. The compounds 18 are cleaved by dilute hydrochloric acid, liberating L-valinate 8 and ( R )-α-alkenyl glycine methyl esters 21 , which on further hydrolysis yield ( R )-α-alkenyl glycines 23 . This synthesis is limited only by the availability of thioketones 14 |
| Starting Page | 1409 |
| Ending Page | 1417 |
| Page Count | 9 |
| File Format | PDF HTM / HTML |
| DOI | 10.1016/S0040-4020(01)82426-1 |
| Alternate Webpage(s) | https://kops.uni-konstanz.de/bitstream/handle/123456789/9661/59_enantioselective.pdf?isAllowed=y&sequence=1 |
| Alternate Webpage(s) | http://kops.uni-konstanz.de/bitstream/handle/123456789/9661/59_enantioselective.pdf?isAllowed=y&sequence=1 |
| Alternate Webpage(s) | https://doi.org/10.1016/S0040-4020%2801%2982426-1 |
| Volume Number | 40 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
