5-Acetyl hydantoin

Aoetylderiyat der Verbindung CfEnN,0, (4.5-Dio n-1.4.S-trimethyl-nydTOuracil Oder Hjnunt des 3.5-I)lmetliyI-6-acetyl-hydantoins) 15 1 486. 

A condensation occurs between 5-hydroxymethylfurfural and malonic ester20 and in a similar way, two molecules of malonic ester react with furan 2,5-dialdehyde.88 A condensation product, XXXV, has also been obtained with hydantoin.89 5-Hydroxymethylfurfural and its acetyl derivative undergo the Perkin reaction with sodium acetate and acetic anhydride giving 5-acetoxymethylfuran 2-acrylic acid (XXXVI).70 Similar products of the same reaction are obtained from 5-methyl-furfural71 and 5,5 -diformyl-l,l -furylmethyl ether (XXVII).61,72... 

The solutes resolved by the Type IV CSPs must be able to form coordination complexes with transition metal ions. This limits the classes of compounds to a-amino acids and mono- and dicarboxylic acids containing an ot hydroxyl moiety. The most common solutes resolved on these CSPs are underivatized amino acids, although a number of derivatized amino acids can be resolved, including W-acetyl, amide, N-carbamoyl, N-carbo-benzoxy, and hydantoin derivatives, as well as complex amino adds such as the biochemical modulator BSD (79). 

A modification of the stepwise degradation of peptides involves their N-terminal cyclization with N,7V -carbonyl- or N,N -thiocarbonyldiimid-azole.120 Acetylation of N-hydroxyphenylurethane (67) yields the diester 68, which by simply heating in refluxing ethanol furnishes the JV-acetoxy-hydantoin 69.121... 

All microorganisms producing D-aminoacylases commonly produce L-aminoacy-lases as well. Therefore, to reach high optical purity of the D-amino acids produced from the respective N-acetyl-D,L-amino acids, the D-aminoacylases have to be separated from the L-aminoacylases (Table 12.3-13). However, this is a disadvantage in view of an industrial application since additional purification steps lead to more expensive enzymes and thus add costs to the whole production process. This is one of several reasons why it is widely accepted today that the production of D-amino acids by enzyme-catalyzed hydrolysis of D,L-hydantoins seems to be more promising than the D-aminoacylase route via N-acetyl-D,L-amino acids. The enzyme-catalyzed synthesis of D-amino acids from the respective D,L-hydantoins is described in Chapter 12.4. 

The first total synthesis of (+)-hydantocidin (1) in an optically active form has established its absolute configuration (Scheme 9). The synthesis was started by aldol condensation of 4-0-benzyl-2,3-C -isopropylidene-D-threose (78) and l-A -acetyl-3-Af-(4-methoxybenzyl)-hydantoin (76) ° in the presence of potassium ferf-butoxide to afford a mixture of Z- and -isomers 79 (71%) and 80 (14%), respectively. Treatment of the mixture of 79 and 80 with p-toluenesulfonic acid afforded the cyclized product 82 and 81. Alternatively, treatment of (2A,3i )-4-benzyloxy-2,3-epoxybutanal (84) with lithium derivative of 77 afforded 85, which upon treatment with lithium bis(trimethylsilyl)amide... 

The hydantoins 47 and 48 are formed directly from the appropriate methylaminopyridine. Methylation, acetylation, or hydrolysis of these compounds gives products analogous to those in the [2,3-6] series. ... 

Enzymatic racemisation is an attractive option in DKR because the reactions catalysed by enzymes are performed under mild conditions. The Degussa group have recently described their successful commercialization of two DKR-based processes that employ racemases, namely (i) the DKR of 5-substituted hydantoins using whole cells coexpressing a L-carbamoylase, a hydantoin racemase and a hydantoinase and (ii) the DKR of N-acetyl amino acids using an acylase in combination with an N-acetyl amino acid racemase from Amycolatopsis orientalis. 

The result is the formation of a stable amide linkage. Other acylations may be accomplished by classical methodology, such as acetylation with acetic anhydride. However, as was observed with alkylations and other reactions, acylations have been developed which readily occur under mild reaction conditions. For example, amino acids will react with isocyanates (R—N=C=0) and isothiocyanates (R—N=C=S) to form hydantoins and thiohydantoins. 

The barbiturate structure resembles that of hydantoins and dialkyl acetyl urea derivatives which are also neuroactive agents (Fig. 4.8). It is clear that the dialkyl substitution at position 5 of barbiturates is essential for their pharmacological activity. Also, if one or two hydrogens are left at position 5 of the barbiturate, the barbiturate will be converted to the trihydroxy pyrimidine derivative, as discussed earlier. 

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