Isoserines

Palladium proved especially useful in the hydrogenation of 2-hydroxy-3-nitropropanoic acid. Reduction over palladium-on-carbon gave pure, powdery isoserine, whereas platinum failed to reduce the nitro function under neutral or acidic conditions reduction over Raney nickel gave a bright green powder (96). 

Bartoli recently discovered that by switching from azide to p-anisidine as nucleophile, the ARO of racemic trans- 3-substituted styrene oxides could be catalyzed by the (salen)Cr-Cl complex 2 with complete regioselectivity and moderate selectivity factors (Scheme 7.36) [14]. The ability to access anti-P-amino alcohols nicely complements the existing methods for the preparation of syn-aryl isoserines and related compounds [67] by asymmetric oxidation of trans-cinnamate derivatives [68]. 

The reaction of silyl ketene acetal addition to nitrones has been used for the synthesis of optically active (2S,3S)-benzoyl- and /V- oc-phenyl isoserine (636a) of isoxazolidine nucleoside-analog of thymine polyoxine C(636b) and of... 

Type I and II silicon-tethered carbonyl-ene reactions were first performed by Robertson.4,4a,4b One particularly striking application of this method is the conversion of isoserine derivative 3 (Scheme 1) into amino triol 4 via a carbonyl-ene reaction followed by Tamao-Fleming oxidation.5... 

Other workers began to study the structure of gramicidin. Christensen and coworkers12 isolated crystalline tryptophane and leucine from a hydrolysate. They found no evidence for a fatty acid component and established that phenylalanine, proline and hydroxyproline were absent from a hydrolysate. These workers isolated alanine diox-pyridate from a hydrolysate and also established that gramicidin contained a compound with vicinal hydroxy and amino groups. They speculated that this compound might be serine or isoserine and proposed that gramicidin contains two tryptophane, 2 leucine, 2 or 3 alanine and 1 hydroxyamino residues or a multiple of this composition. 

Hotchkiss114 isolated optically and analytically pure d-leucine from the hydrolysate. This was the first non-enzymatic proof that d-amino acids actually occurred in gramicidin. He also noted the presence of an amino-hydroxy compound, but indicated that it was not isoserine. 

E. Fischer und W. A. Jacobs. Uber die optisch-aktiven Formen des Serins, Isoserins, und der Diaminopropionsaure. Ber, 1907, 40, 1057-1070. 

Molecular dynamic and NMR studies have shown that only the extended conformation of CF3-acetyldocetaxel (i.e., in which the isoserine side chain is distant from the baccatine moiety) is independent of the hydrophilic or hydrophobic nature of the medium. In the other derivatives of Taxol, the globular conformation is largely favored by a protic medium. " Thus, it would be interesting to perform studies of complexes with tubuhnes in the solid phase to determine if the cytotoxic activity is connected with the conformation. 

Diaz, M. Ortuno, R. M. Enantioselective synthesis of novel homochiral a-substituted (S)-isoserine derivatives. Incorporation of this amino add in a highly conformationally con- 356 strained dipeptide surrogate. Tetrahedron Asymmetry 1996, 7, 3465—3478. 

R,3S)-p-Phenyl-isoserine methyl ester (4.35 g, 22 mM) is dissolved in dry THF (100 ml) and the flask cooled to 0°C. To the mixture is added t-butyl isocyanate (2.8 ml, 25 mM). TLC after 15 min shows some starting material left so additional isocyanate (0.5 ml) is added. TLC after 1 h shows no starting material so the solvent is concentrated under reduced pressure to give the N-(t-butylaminocarbonyl)-p-phenyl isoserine methyl ester. 

Wang, M.X., Deng, G., Wang, D.X., et al. 2005. Nitrile biotransformation for highly enantioselective synthesis of oxiranecarboxamides with tertiary and quaternary sterocenters efficient chemoenzymatic approaches to enantiopur a-methylated serine and isoserine derivatives. Journal of Organic Chemistry, 70 2439-44. 

Recently, Ojima et al. described the synthesis of some taxanes with C-13 fluorine-substituted isoserine side chains. In pharmaceutical practices, the fluorine atom is usually introduced as an isosteric atom of the hydrogen atom, but it showed higher or sometimes unique activity against its hydrogen-containing counterparts. Flourine also blocks the metabolism of the parent molecule, which led to the... 

A series of 14p-hydroxy and 14p-acyloxy taxoids 34 with lOp, 5a, 2a-acetoxy, or hydroxy substitutions without C-13 oxygenations and oxetane D ring have been isolated from the cell culture of T. yunnanensis. Attachment of the A-benzoylphe-nyhsoserine side chain to C-14, and incorporation of the 4(20), 5-oxetane ring and change of 2-acetate did not improve their activity. The fact that all derivatives are far less active than paclitaxel prompted the authors to suggest that C-14 isoserine isomers did not bind to tubulin properly. 

Ojima, I. Lin, S. Efficient asymmetric syntheses of P-lactams bearing a cyclopropane or an epoxide moiety and their application to the syntheses of novel isoserines and taxoids. J. Org. Chem., 1998, 63 224-225. 

EDCCl is also used in the N-formylation of isoserin 690 with formic acid to give the N-formyl derivative 691. ... 

---