ISSN:
1434-193X
Keywords:
2-tert-Butylhydropyrimidinones
;
3-Aminocarboxylic acid derivatives
;
Cyclic imino esters
;
Lithium enaminates
;
Alkylations
;
β-Amino acids
;
Asymmetric synthesis
;
Kinetic resolution
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
-Racemic and enantiopure 2-tert-butyltetrahydropyrimidinones (from pivalaldehyde and 3-aminocarboxylic acids) are converted to Alloc-, Boc-, and Z-protected cyclic imino esters (7-10, Schemes 2-4). These are deprotonated to Li enaminates (K, L). Reactions with electrophiles (prim., sec. alkyl, allyl, benzyl, propargyl halides, aldehydes, imines, enoates) give good yields and are highly diastereoselective (products 11-42, Schemes 5-10). A two-step cleavage (removal of protecting group and hydrolysis) under very mild conditions converts the heterocyclic products to α-branched β-amino acid methyl esters (43-61, Schemes 11-13). The structure of the products is determined by NMR spectroscopy (Figure 1), by chemical correlation (Scheme 14), and by X-ray analysis (Figure 2, 3, 7, Table 1). A structure of the Li enaminates is proposed (Figure 4). Mechanistic models are derived for the reactions occurring with formation of two stereogenic centers with relative topicity like (Figures 5, 6).
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
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