Selektive Umfunktionalisierung der terminalen Amidgruppe offenkettiger Polyamide via 2‐Oxazolin‐5‐one als Zwischenstufen. Vorläufige Mitteilung

Abstract

Selective Modification of the Terminal Amide Group of Linear Polyamides via 2-0xazolin-5onesas Intermediates SummaryTreatment of aqueous or alcoholic solutions of diamides of type 2 with HC1 leads to the formation of amide-acids and amide-esters of type 3 (Scheme I and Table). It has been shown, that 2-oxazolin-5-ones of type 4 are intermediates of this selective transformation of the disubstituted terminal amide group. The selectivity of the transformation is demonstrated by the reaction sequence shown in These results show the usefulness of the dimethylamide group as a protecting group for carboxylic acids for example in the peptide synthesis.Wie schon vor langerer Zeit berichtet worden ist [I], reagiert 3-Dimethylamino-2,2-dimethy1-2 H-azirin (1) mit Carbonsauren schon unterhalb Raumtemperatur zu Diamiden des Typs 2 (Schemal). Die glatte und nahezu quantitative Bildung von 2 wird via das Primaraddukt a und dessen Umwandlung zum Zwitterion b formuliert.In Zusammenhang mit der Verwendung von Aminoazirinen des Typs 1 als Bausteine fur die Synthese von Heterocyclen (vgl. [2] [3]) stellte sich das Problem, die terminale Amidgruppierung in Molekeln des Typs 2 selektiv in eine Ester-bzw. Thioesterfunktion unter Bildung von 3 uberzufiihren.Beim Einleiten von getrocknetem HC1-Gas in eine athanolische Losung des aus 1 und Benzoesaure erhaltenen N,N-Dimethyl-2-benzoylamino-2-methyl-1)

Carbamoyl Anion Addition to N-Sulfinyl Imines: Highly Diastereoselective Synthesis of α-Amino Amides

“…The amide moiety of the products could conveniently be converted to an ester or amine (Scheme ). The ester conversion was accomplished by the oxazolone procedure of Heimgartner . Deprotection of the sulfinyl group of 21 and subsequent N-benzoylation afforded diamide 37 .…”

Asymmetric Synthesis of 4,4-Disubstituted-2-Imidazoli-dinones: Potent NK1 Antagonists

“…Hydrolytic cleavage of bulky disubstituted imidazolidinones can be quite problematic, particularly for substituents larger than methyl on the phenylglycine system (ref a,b). The structural requirements for our compounds were not tolerant of these conditions.…”

“…The initial synthetic implementation of our strategy utilized the N -benzoyl-protected imidazolidinone; however, we encountered problems with the extreme conditions needed to hydrolyze the benzoyl group of the dialkylated N -benzoyl-imidazolidinones. , To circumvent this problematic cleavage, we sought to explore the “unprotected” imidazolidinone 13 (Scheme ). ,

3 Alkylation of Imidazolidinone 13

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Synthesis of Macrocyclic Lactones via Ring Transformation of 4‐(ω‐Hydroxyalkyl)‐1,3‐oxazol‐5(4H)‐ones

“…We became interested in 1,3‐oxazol‐5(4 H )‐ones as intermediates in the ‘azirine/oxazolone method’ for the synthesis of peptides containing α , α ‐disubstituted α ‐amino acids . It has been shown that peptides of type 1 with a C‐terminal Aib‐amide on treatment with HCl in toluene at elevated temperature form 1,3‐oxazol‐5(4 H )‐ones 2 , which in the presence of nucleophiles spontaneously react under ring opening to give, e.g ., esters 3 [a][6c][6d] ( Scheme ). Furthermore, it was proposed that the DCC‐coupling of peptides containing a terminal Aib‐acid with amino acid esters 4 leads to peptides 5 via an intermediate 1,3‐oxazol‐5(4 H )‐one 2 [b – 6e] ( cf .…”