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  • 1
    ISSN: 0170-2041
    Keywords: Amino acids ; Peptides ; Cyclopropanes, silylamino- ; Condensation, fluoride-induced ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The N-silylated methyl 2-aminocyclopropanecarboxylate 1 can be incorporated into a dipeptide via a CsF-mediated condensation reaction with N-tosylated phenylalanine chloride 5. Due to its instability the corresponding free β-amino acid 4 could not be isolated up to now, and peptides containing this structural element have previously not been accessible. After desilylation, the aminomethyl-substituted cyclopropane or cyclopropene derivatives trans- 10, 12, and 13 also provided N-protected dipeptides in good yields.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0170-2041
    Keywords: Amino acids ; GABA analogues ; Aminocyclopropanes ; Enamines, N-silylated ; [2 + 1] Cycloaddition ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An Efficient Route to GABA-Analogous Amino Acids: Cyclopropanation of N-Silylated Allylamines and EnaminesN-Silylated allylamines 1 are effectively transformed into methyl cyclopropanecarboxylates 2 by methyl diazoacetate under Rh2(OAc)4 catalysis. Derivatives 2a and 2b are smoothly converted into trans-substituted amino acids 6a and 6b, respectively, and to bicyclic γ-lactams 5a and 5b. The pharmacologically interesting γ-aminobutyric acid (GABA) analogue trans-6a is now available in few steps. Photochemical and thermal Fe(CO)5-induced hydrogen shift converts allylamine derivatives 1 into N-silylated enamines 7. While enamine (E)-7a can be cyclopropanated with methyl diazoacetate under Cu(acac)2 catalysis to afford the desired cyclopropane derivatives 8a in good yield, the other enamines are rather unreactive towards the carbenoid. Use of an optically active catalyst provides 8a with an ee of 56% (cis) and 20% (trans). Acid-induced ring cleavage of 8a gives the β-formyl ester 10a, and reduction of 8a followed by desilylation provides the aminocyclopropane 14 in good overall yield, thus demonstrating that cyclopropanes like 8a can serve as useful synthetic intermediates.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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