Diaminocarboxylic acids

The aza-Michael reaction yields, complementary to the Mannich reaction, P-amino carbonyl compounds. If acrylates are applied as Michael acceptors, P-alanine derivatives such as 64 and 65 are obtained. The aza-Michael reaction can be catalyzed by Bronsted acids or different metal ions. Good results are also obtained with FeCl3, as shown in Scheme 8.29. The addition of HNEt2 to ethyl acrylate (41f), for example, requires 10mol% of the catalyst and a reaction time of almost 2 days [94], The addition of piperidine to a-amino acrylate 41g is much faster and yields a,P-diaminocarboxylic acid derivative 65 [95]. 

Condensation of 1,2-diaminopropane and 2,3-dioxobutane similarly gives 5,6-dihydro-2,3,5-trimethylpyrazine which is oxidized to the corresponding pyrazine in 58% yield by treatment with potassium hydroxide pellets.111 Hydroxypyrazines are very conveniently prepared from a,j8-dicarbonyl compounds and a-amino acid amides [Eq. (1)],30,112 and pyrazinecarboxylic acids have been prepared by condensation of an a,)5-diketone with an a,/ -diaminocarboxylic acid, followed by oxidation (Scheme 2). Thus, condensation of benzil and... 

Anion-active polyurethane-semicarbazides XIX are obtained using bifunctional anion-containing chain extenders, such as dihydroxy- or diaminocarboxylic acids, dihydroxy- or diaminosulfoacids [9] ... 

The reaction between 2-nitrothiophen and secondary aliphatic amines leads most probably to the ring-opened product (213). Raney-Nickel desulphurization continues to play an important role in the structure determination of thiophen derivatives, and for the synthesis of macrocyc-lic compounds, such as a-alkylcycloalkanones, amino-lactams of aliphatic diaminocarboxylic acids, and of dethiobiotin. The nickel boride catalyst (NiBo), prepared from nickel(ii) chloride and sodium borohydride in methanol, gives olefins in 50—55% yield. From (214) a mixture of methyl... 

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