L-serine derivatives

C-N.m.r. Chemical-shift Data for Various a- and /J-D-Glycosyl-L-serine Derivatives... 

In a synthesis of the L-serine derivative 133, Kunz and Buchholz100 treated N-(benzyloxycarbonyl)-L-serine 2-bromoethyl ester (135) with tetra-O-benzoyl-a-D-glucopyranosyl bromide (136) protection of the... 

To carry out 1,3-dipolar cycloadditions with alkyl acrylates, nitrones of various structures such as ferrocenylnitrones (141), nitrones derived from chiral amino acids (210), L-serine-derived nitrones (660) and N -substituted C -phosphorylated nitrones (263) have been used. 

Likewise, the galactosylation of O-glycopeptide derivatives 189-191 to give O-lactosamine - L-serine derivatives (192-194) using (1 - 4)-/ -d-... 

On the other hand, in contrast with the non-Kolbe reaction of (113), that of L-serine derivative (115) gave an optically active a-methoxylated product (116) with 39% ee when graphite was used as the anode... 

Hoechst has reported an enantioselective approach toward the key azabicyclo[3.3.0] octane-3-carboxylic acid 46 that preserves the stereochemistry of the L-serine-derived starting material (Urbach and Henning, 1991). L-Serine methyl ester (48) was alkylated... 

An alternative and elegant approach to bicyclo[3.3.0]isoxazolidines from alkenyl oximes was developed by Grigg (205) and applied in asymmetric reactions by Hassner et al. (206-209) and others (210). The optically active L-serine derived oxime 130 was proposed to be in a thermal tautomeric equilibrium with the nitrone tautomer 131, which underwent an intramolecular 1,3-dipolar cycloaddition to form the product 132 in 80% yield as a single stereoisomer (Scheme 12.44) (209). 

Izumiya and co-workers (77JA8346) have undertaken a systematic study of the chiral induction on hydrogenation (H2,l atm., Pd black, MeOH) of a series of cyclodipeptides of the type cyclo(L-aminoacyl-Dha), where Dha represents dehydroalanine. These were synthesized from the corresponding L-serine derivatives the final dehydration was accomplished by Photaki s procedure (63JA1123). Contrary to the report of the earlier workers, the de in the product cyclo(L-aminoacyl-Ala) [(S,S) over (S,R) was the highest with valine (98.4%) and the least with proline (84.8%). Leucine gave about 95% de. 

The excellent nucleofugal properties of the imidazylate group has been used in the intramolecular cyclization of derivatives of -substituted L-serine derivatives, leading to p-lactams [105,106] (Scheme 18). 

Enterobactin was originally isolated from bacterial cultures of Salmonella typhimurium or Escherichia coll by lengthy extraction and chromatographic purification procedures giving yields in the region of 15 mg of product per litre of nutrient solution. Understandably, the exacting nature of this procedure has led to the development of a number of laboratory procedures to produce enterobactin synthetically. The most efficient of these makes use of the template effect (Section 3.9.1) involving the trimerisation of bulky triphenylmethyl substituted L-serine derivative about a tin atom (Scheme 3.28). 

There are several types of evidence that the L-serine derivative that activates the a reaction is the Schiff base formed between aminoacrylate and pyridoxal phosphate (ES III in Fig. 7.6). (1) Amino acids including l- or D-tryptophan and glycine that form tetrahedral,... 

The addition of allylmagnesium bromide to the serinal derivative 38 is syn selective in the presence of (—)-p-methoxydiisopinocampheylborane, giving the erythro derivative 156 (Scheme 13.55). Methylation of the alcoholic moiety of 156, followed by ozonolysis with reductive workup, hydrolysis of the carbamate and acidic treatment forms the methyl glycoside 157 of the E-ring moiety of calicheamicin [61]. A similar approach was proposed by Roush starting from the L-serinal derivative 50 [102]. 

Poll and Sames [112] have converted L-serine into A -methylfucosamine (Scheme 13.63). The method relies on the diastereoselective addition of propenyllithium to the aldehyde derived from protected L-serine derivative 183, giving allylic alcohol 184. Catalytic osmylation of 184 gives a 6 1 mixture of anti,syn 185 and syn,syn-2iminotnols. Protection of the triol 185 as its triacetate, reductive methylation and desilylation provides 186. Successive Swern oxidation, methanolysis and benzhydryl group hydrogenation leads to A -methylfucosamine 187. 

An elegant total synthesis of the semiprotected form of lincosamine was realized by Marshall and Beaudoin [116]. An aldehyde derived from destomic acid (6-amino-6-deoxy-L-g/yc ro-D-ga/acto-heptonic acid) was derived in a similar way from a L-serinal derivative via hetero Diels-Alder addition to 1-ethoxy-3-[(trimethylsilyl)oxy]-4-benzyloxy-1,3-butadiene [142]. A similar method was applied to the preparation of a semiprotected form of anhydrogalantinic acid, a component of the antibiotic galantin I [142]. 

Some reactions can be driven to completion by removing the products physically from the reaction. Products that are out of solution may be protected from further reaction. An excellent example is found for the selective removal of the Boc (t-butyloxycarbonyl) group from N-Boc-amino acid t-butyl esters [37]. As shown in Figure 4.14, treatment of the L-serine derivative 18 with anhydrous HC1 in... 

Similarly, at 1.0 GPa the L-serine derivative 108 undergoes quantitative hydrolysis to the acid 109 enantioselectively and chemoselectively hydrolysis does not occur at atmospheric pressure (Scheme 7.27). 

The addition of the L-serine derivative 6 to dienes 1 or 5 gives pyrones. yi -7 and anti-8 with good to excellent diastereoselectivities46. 

Condensation between tetra-O-acetyl-a-D-galactopyranosyl bromide and a suitably protected 2-acetamido-2-deoxy-0 -D-galactopyranosyl-L-serine derivative gave access to compound (48) which is the JV-tosyl derivative of the carbohydrate core of mucins and was required for studies of haemagglutination. Evidence that the major glycoprotein of TA3-Ha tumour cells contains the same disaccharide was produced by the isolation, after alkaline degradation and sodium borohydride reduction, of 2-acetamido-2-deoxy-3-On 3-D-galacto-... 

Two dimers, the galactosyl bromide 2,4,6-tri-C -benzoyl-3-0-(2,3,4,6 tetra-(9-benzoyl- 8-D-galactopyranosyl)-a-D-galactopyranosyl bromide, and the D-xylosyl-L-serine derivative, 2,3 -di-0-benzoyl- 3-D-xylopyranosy 1)tAT-carbobenzyloxy-... 

From Aminoacids - The synthesis of a constituent amino-sugar of calichea-micin by asymmetric allylboronation of an L-serinal derivative (Vol. 29, p. 131) has been reviewed. (+)-Elsaminose 39, a constituent of the antibiotic elsamicin A, was synthesized from the L-threonine-derived D-thneose derivative 38 (Scheme 10). ... 

Diamino-2,4-dideoxy-L-arabinose and -L-ribose, 75 and 76 respectively, were obtained in similar quantities by chain extension of the L-serine-derived aldehyde 74 as shown in Scheme 17. The imino-sugar glycosylamide 78 was... 

The aminoalditol 23 was prepared by a pinacol-like homocoupling of an appropriately protected L-serine-derived aldehyde and promoted by a vanadium-zinc complex [V2Cl3(THF)6)]2[Zn2Cl6]. (See Section 2.2 for the further transformation of compound 23). 

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