Dehydro alanine

It appears that the molybdenum catalyst is more suited to the cross-metathesis of the sterically bulky vinylglycines. The cross-metathesis reaction of a similarly protected dehydro alanine gave only recovered starting material. 

The main genera responsible for freshwater toxic blooms are Microcystis, Anabaena, Aphanizomenon and Oscillatoria. Toxins produced include 1. anatoxins, alkaloids and peptides of Anabaena 2. the peptide microcystin and related peptides of Microcystis 3. aphantoxins, compounds of Aphanizomenon with properties similar to some paralytic shellfish poisons. Properties of Oscillatoria toxin suggest they are peptides similar to those of Microcystis. Microcystis toxins are peptides (M.W. approx. 1200) which contain three invariant D-amino acids, alanine, erythro-3-methyl aspartic and glutamic acids, two variant L-amino acids, N-methyl dehydro alanine and a 3-amino acid. Individual toxic strains have one or more multiples of this peptide toxin. The one anatoxin characterized is a bicylic secondary amine called anatoxin-a (M.W. 165). The aphantoxin isolated in our laboratory contains two main toxic fractions. On TLC and HPLC the fractions have the same characteristics as saxitoxin and neosaxitoxin. 

Stable isotope methodology has been applied to the study of the biosynthesis of madumycin II (A2315A, 92) in Actinoplanes philippensis (60, 64). As with virginiamycin Ml (90), carbons 2, 26, 27, and 28 were found to be derived from valine, C-29 from methionine, C-3 to C-6 from acetate, N-7, C-8, and C-9 from glycine, carbons 10 to 17 and C-31 from acetate, and N-18, C-19, C-20, 0-21, C-32, and 0-34 from serine. The origin of the D-alanine residue, N-23, C-24, C-25, C-35, and 0-36, was of particular interest in this study. No incorporation of DL-[U-13C]serine was observed in the alanine portion of the molecule, eliminating the intermediacy of the a,(3-dehydro alanine unit 101 derivable from the acylserine precursor 100. This was corroborated by the observed incorporation into the molecule of intact doubly labeled L-[3-l3C,3,3,3-2H]alanine. dl-[1-l4C]Alanine was also efficiently incorporated. These results and those from de-... 

Lantibiotics are small, membrane-active peptides (< 5 kDa) containing the unusual amino acids lanthionine, P-methyl-lanthionine, and the dehydrated residues dehydro alanine and dehydrobutyrine e.g. nisin, lacticin 481, carnocin U-149, lactocin S, sublancin 168 [29-38]. The intrachain positioning of these polycyclic structures of the lantibiotics has been used to group them into linear (Group lA) or circular (Group IB) lantibiotics [39]. Based on similarities in the... 

Chemical inhibition of L-phenylalanine ammonia lyase activity may be achieved by the use of typical carbonyl reagents such as sodium borohydride and potassium cyanide. Treatment of the enzyme with tritiated sodium borohydride and subsequent hydrolysis gave alanine in which the majority of the radioactivity was confined to the jj-methyl group . Similarly reaction with potassium cyanide and hydrolysis gave aspartic acid labelled exclusively in the -carboxyl group . These observations led to the proposal that the active site of the enzyme, like that of the related L-histidine ammonia lyase , contains a dehydro-alanine residue... 

Havir and Hanson have proposed a mode of action for the enzyme in which the first step in the enzymic catalysis is the addition of the amino group of L-phenylalanine to the methylene group of the dehydro-alanine residue. Figure 5.2. Cinnamate (17) is first released from the enzyme in the elimination step and the amino enzyme (44) can then either hydrolyse to release ammonia or react with cinnamate to regenerate L-phenylalanine. 

The linkage in madumycin II (92) of the D-alanine and oxazole residues (the latter thought to arise by cyclization of an acyldehydroserine) is considered significant insofar as the cooccurrence of d- and dehydro amino acids in microbial compounds had been previously noted (61), and a possible relationship between these systems suggested. Several microbial metabolites which display antibiotic properties incorporate a,(i-dehydro amino acids and their derivatives (62). 

III this case the two steps, 3-eliminati6n and hydrolysis of the resulting dehydro enzyme were done simultaneously. This procedure may facilitate the task of establishing the chemical structure of the active site of esterases and peptidases (cf. Cohen et al., 1959 cf. TomaSek et al., 1960 Sanger and Shaw 1960). Complications may arise here through base-catalyzed dis-mutations of pyruvoyl peptides, which are observed in the conversion of pyruvoylglycine into alanine by the action of base (Fu et al., 1952 cf. Wieland et al., 1958). 

The ( )-isomers of N-acyl-a-dehydro(l-naphthyl)alanines (125 n = 2,3 R = Me, Ph R = Me, Et, Pr) produce l,2-dihydrobenzo[f]quinolines (126) by an electron-transfer reaction, and the )- and (Z)-isomers produce minor amounts of the benzo[f]isoquinoline (127) and 1-azetidine derivatives respectively by an intramolecular photoaddition. Evidence suggests that the bulky diisopropylamino donor and the N-benzoyl group enhance the relative yield of (127) to (126). 

An alternative method for driving the reaction equilibrium of transaminations was developed by Hohne et al. (Figure 14.44) [65]. Alanine served as the amine donor, and pyruvate decarboxylase was used to remove the pyruvate coproduct by decarboxyl ation to acetaldehyde. An advantage of pyruvate decarboxylase over lactate dehydro genase is that it requires no cofactor recycling system, and the high volatility of the coproducts allows for the desired shift of equilibrium. 

The Hartwig-Buchwald arylation of amines can also be favorably combined with the Heck reaction [383, 384]. For example, the intramolecular palladium-catalyzed N-arylation of immobilized dehydro(halophenyl)alaninate was found to proceed smoothly to form indolecarboxylates. The method was successfully combined with the Heck reaction to constitute a one-pot indole synthesis in the form of a palladium-catalyzed cascade C,N-arylation reaction (Scheme 8.58) [383, 384]. 

Use. When the reactivity of 4-bromoacetamidoestrone methyl ether was examined, n-cysteine, L-methionine, L-histidine, L-lysine, n-trypto-phan, L-tyrosine, and A-acetylhistidine were shown to be alkylated by the steroid derivative, but alanine was not. Assay revealed that 4-bromoacetamidoestrone methyl ether is a substrate for estradiol 17 -dehydro-genase and thus binds at the active site. It has a K of 0.14 mAf. Radioactive 4-bromoacetamidoestrone methyl ether (0.2 mAf) was used to... 

This peptide is formed by several strains of Streptococcus lactis (Langfield-N-group). It contains a number of unusual amino acids, namely dehydroalanine, dehydro-P-methy 1-alanine,... 

Pd on poly-L-leucine and other poly-L-a-amino-acids hydrogena- tion Precursors (S)Phenyl-alanine, (R)dehydro-oc-methylcinnamic acid (see Figure 7) 1.16-5.94 [83-86]... 

Some aminobenzoic acid diuretics containing the thiophen ring have also been studied. The syntheses and lipid-lowering properties of (203) and (204) have been described. 3-j8-(2-Thienyl-alanine-8-lysine)vasopressine has been synthesized by the solution technique. A comparison of the bioavailability of [2,5- C]thiophen after oral and rectal administration in mice has been reported. The nitro-reduction of carcinogenic 5-nitro-thiophens by rat-tissues has been studied. Thiophen-ring-containing compounds with antiradiation, antidepressant, antiparasitic, " antibacterial, - antiviral, and broncho-dilator activity have been studied. A thia-steroid, 14,15-dehydro-A-nor-3-thiaequilenin, has been synthesized. In connection with studies on the syn-... 

Motohashi, X, Maekawa, K., Kubo, K., Igarashi, X, and Sakurai, X, An efficient transformation of substituted N-acyl-a-dehydro(l-naphthyl)alanines into l,2-dihydrobenzo[f]quinolinone derivatives via photoinduced intramolecular electron transfer. Heterocycles, 57, 269-292, 2002. 

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