Serine products derived from

The identities of the two VL complexes are not known with certainty, but the available evidence suggests the -557 ppm-type products arise from monodentate reaction at the carboxylate group, whereas the -544 ppm products derive from monodentate reaction at the nitrogen functionality. Additional products from amino acids with reactive sidechains, as found in serine or aspartic acid, have not been reported.51V chemical shifts for products formed with histidine are similar to those observed for other amino acids, except that an additional signal (-571 ppm) has been observed [66],... 

An example of cyclization using chiral radicals derived from natural products is given in the 5-exo-dig radical cyclization of A-alkynyl sulfonamide 53 derived from 2(5)-serine to give 2(5)-4-exomethyleneproline 54 (equation 43). The exomethylene product has been recovered without any detectable directly reduced, noncyclized product or product derived from an endo cyclization. 

Secondary products derived from glycine, L-serine, and L-alanine (D 10)... 

D 10 Secondary Products Derived from Glycine, L-Serine, and l-Alanine... 

In NRPs and hybrid NRP-PK natural products, the heterocycles oxazole and thiazole are derived from serine and cysteine amino acids respectively. For their creation, a cyclization (or Cy) domain is responsible for nucleophilic attack of the side-chain heteroatom within a dipeptide upon the amide carbonyl joining the amino acids [61]. Once the cyclic moiety is formed, the ring may be further oxidized, to form the oxazoline/thiazoline, or reduced, to form oxazolidine/thiazolidine (Figure 13.20). For substituted oxazoles and thiazoles, such as those... 

New methods for the synthesis of 2,4-disubstitued oxazoles are summarized in a recent review. 2-Alkyl-1,3-oxazoles bearing alkyl, aryl, or acyl substitution at C4 are common substructures in natural products. Examples include macrolides such as rhizoxin (4), hennoxazole A (5), and phorboxazole A (6), ° as well as many cyclic peptides that incorporate an oxazole subunit presumably derived from serine. ... 

In 2002, the condensation of the titanium enolate derived from 2-pyridylthio acetoxyacetate with /V-4-methoxvphenvlimine of (S)-0,0-cyclohexylidene protected glyceraldehyde has been reported to give (35.4/C4 A)-p-lactam as a single product in 65% isolated yield (Scheme 52), [137]. A reactions sequence at C-3 and C-4 led in good yield to the p-lactam inhibitor of the serine protease prostate-specific antigen. 

In the dihydroxylation of cyclohexene by Me3N+—O-, catalysed by OsC>4, aromatic amines and aliphatic chelating (TMEDA) or bridging (DABCO, hexamine) amines were found to retard the oxidation, owing to the formation of amine adducts of the dioxomonoglycolatoosmium(VI) ester intermediates, which are more resistant to the further oxidation required for product formation.98 Alkenes derived from Gamer s aldehyde, A-Boc-/V,0-acctonide of the aldehyde of L-serine, may be dihydroxylated by OsC>4 with excellent selectivities that may be explained by A1,3 strain.99... 

P-Elimination and then replacement reaction of an a-amino acid with a nucleophile is very attractive from the viewpoint of synthetic organic chemistry because various P-substituted alanines may be prepared from a simple a-amino acid, such as serine, and nucleophiles. A reaction catalyzed by tryptophan synthase - the formation of tryptophan from serine and indole - is one of the most well-known P-elimination and replacement reactions (Scheme 2.7). Here, an aldimine Schiff base is derived from reaction of the enzyme-bound PLP with serine, which then dehydrates to give the Schiff base of PLP with 2-aminoacrylate. Indole then adds to the vinyl Schiff base, generating tryptophan after lysine aminolysis of the Schiff base product. 

Alteplase [AL te place] previously known as tissue-type plasminogen activator (tPA), is a serine protease originally derived from cultured human melanoma cells. It is now obtained as a product of recombinant DNA technology. 

This cyclization has been used for a synthesis of enterobactin (5), a natural iron carrier (previous synthesis, 8, 215-216) by cyclization of a linear trimer of serine. Thus the lactone 3, derived from i.-serinc, cyclizes in the presence of 1 to the tricyclic lactitnc 4 in 23% yield. This product was converted into 5 by dctritylation and acylation. ... 

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