Piperazinediones Diketopiperazines

Preparation of diketopiperazine as part of a bicyclic system was developed by a one-pot Ugi-4-center-3-component reaction (U-4C-3CR) [50]. A 3-keto or aldo acid 155 was used as bifunctional educt for an intramolecular Ugi reaction forming a five-membered ring. The application of C-protected amino acids 156 as amine components enables an intramolecular cyclization forming 2,6-piperazinediones 158 (Scheme 26). 

Throughout this article, the heteroring will be referred to as either piperazine-2,5-dione or occasionally as cyclodipeptide. The earlier practice of referring to the ring as diketopiperazine has been avoided. The numbering of the piperazinedione ring is as shown in (1). In the cyclodipeptide nomenclature, the common three-letter code for the two amino acids, with the necessary prefix to indicate absolute configuration, will be used. 

The methodology was successfully extended to a one-pot total synthesis of complex heterocyclic systems such as pyrazino [2,1-b] quinazolines 79, encountered in nature as alkaloids 80-82 (Scheme 50) [125]. To assemble the pyrazino[2,l-fo]quinazoline core, N-Boc protected amino acid 76 was employed instead of carboxylic acid 72 (Scheme 49) in the synthesis of the corresponding intermediate benzoxazinones 77. The subsequent reaction with an amine moiety of another amino acid ester 78 was accompanied by concomitant cleavage of the N-Boc protecting group and diketopiperazine-like cyclization (for the one-pot deprotection-cyclization reaction of N-Boc dipeptide esters to afford 2,5-piperazinedione under microwave dielectric heating, see [128]) to afford the target heterocycle 79. Hence, the total... 

Piperazinedione, usually called 2,5-diketopiperazine, can be prepared by heating either glycine (e.g., in glycerol) or glycine ethyl ester hydrochloride.41 An equilibrium between A-methylenemethyl-amine (MeN=CH2) and its cyclic trimer (25a) is known to favor the latter... 

Diimide = diimine = N2H . See Diazene Diisopropylamine etc. See 2-Propaneamine,... etc. Diketones. See Dioxo compounds Diketopiperazines = 2 -piperazinediones, 237 Dilution. See High-dilution methods 1,4 5,8-Dimethanonaphthalene, 1,2,3,4,10,10-hexachloro-l,4,4a,5,8,8a-hexahydro-,... 

An iron(III)-binding compound with the properties of a secondary hydroxamic acid has been isolated from supernatant solutions of iron-deficient cultures of a red yeast, Rhodotorula pilimanae (Atkin and Neilands, 1968). The compound rhodotorulic acid (CXVIII) was characterized as LL-3,6-bis (JV-acetyl-3-hydroxyaminopropyl)-2, 5-piperazinedione, i.e., the diketopiperazine of -JV-acetyl-L-5-N-hydroxyomithine. The latter is an amino acid which is a constituent of ferrichromes, albomycins, and fusarinines. In the characterization of rhodotorulic acid, IR, UV, NMR, ORD, and mass spectroscopy were applied. 

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