Amino Acids through Piperazine-2,5-diones

Catalytic deamination of diethylenetriamine (86) over kaolin and alumina with some acidic admixtures at 280-400° to give pyrazine, piperazine, and other products has been examined (476). The conversion of a-amino acids, through piperazine-2,5-diones, with phosphoryl chloride to pyrazines has been discussed in Section IN. 

The preparations of hydroxypyrazines by primary syntheses have been described in Chapter II, and are summarized briefly, together with further data, as follows Section II.IG, from the reaction of a, 3-dicarbonyl compounds with ammonia [282 (cf. 281, 280), 283, 285] with additional information (1042, 1043) Section II.IM, from 1,2-dicarbonyl compounds with a-amino acids (311) Section II.IN, from a-amino acids through piperazine-2,5-diones (93,95,101,282,312,313)with additional data (843) Section 11.10, from aldehyde cyanohydrins ( ) [317-319 (cf. 282)1 and Section II.IP, from o-nitromandelonitrile and ethereal hydrogen cyanide (325). The preparations from a,iJ-dicarbonyl compounds with a,/ -diamino compounds are described in Section 11.2 (60, 80, 358, 359, 361-365b, 365d, 366-375) additional data have also been reported (824, 825, 827,845,846,971, 1044, 1045) and some reaction products have been isolated as the dihydro-pyrazines (340,341,357). 

Dihydropyrazines may be prepared by the self-condensation of o -(primary amino)carbonyl compounds and some of these syntheses have been described in Sections II.lA (169, 172, 178, 186, 190), Il.lJ (294-298), and II.IL (306). The conversion of a-amino acids through piperazine-2,5-diones (2,5-dihydroxy-3,6-dihydropyrazines) to pyrazines has been described in Section II.IN (93, 95, 101, 282, 312-314a) and Section II.6 (314, 314a) and ring transformations to 2,5-dihydropyrazines in Section II.9 (302, 505a, cf. 1541). 3-Phenylazirine dimerizes on standing to 2,5-diphenyl-3,6-dihydropyrazine (1577). 

Amino acids. Through enolization piperazine-2,5-diones and perhydropyrim-idin-4-ones using LHMDS as the base for alkylation, a- and /3-amino acids are synthesized, respectively. The stereoselectivity can be manipulated by varying chiral substituents on the nitrogen atoms. 

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