Synthesis sugar derivs

Various substituted N-hiomo- and A/-chloroureas have also been prepared (97). These compounds are useful for synthesis of oxazoUdinones, and also hydrazine, hydrazo, and azo compounds. A/-Bromourea [51918-81 -1] is useful for selective oxidation of sugar derivatives (98). 

BAER FISCHER Amino sugar synthesis Synthesis of 3-nrtro and 3-amlno sugars by aldol condensation of sugar-derived dlaktehydes with nilroalkanes. 

An attractive feature in this reaction is the possibility of direct substitution and formation of unblocked sugar derivatives containing one or more chlorodeoxy function in essentially two steps. Another facet is the formation of methyl 4,6-dichloro-4,6-dideoxy-hexosides from certain methyl glycosides in one step. Such compounds could be valuable intermediates in the synthesis of dideoxy and diamino sugars of biological importance. 

The Action of Alkaline Reagents on 2 3-1 6- and 3 4-l 6-Dianhydro-3-talose. A Constitutional Synthesis of Chondrosamine and other Amino-Sugar Derivatives, S. P. James, F. Smith, M. Stacey, and L. F. Wiggins, J. Chem. Soc., (1946) 625-628. 

The mono-silylated or free acetamides, which are liberated during silylation with 22 a, can, furthermore, interfere with any subsequent reaction, e.g. with electrophiles. Thus in the one-pot/one-step silylation, Friedel-Crafts catalyzed, nucleoside synthesis starting from protected sugar derivatives and pyrimidine or purine bases, the mono- or bis-silylated amides such as 22 a can compete with less reactive silylated heterocycHc bases for the intermediate electrophilic sugar cation to form protected 1-acetylamino sugars in up to 49% yield [42, 47]. On silylation with trimethylsilylated urea 23 a the Hberated free urea is nearly insoluble in most solvents, for example CH2CI2, and thus rapidly precipitated [43]. 

The Mukaiyama condensation method was also utilized in the synthesis of several antibiotics and related bioactive substances. These syntheses include apramycin, using 4-azido-2,3,6-tri-(P-benzyl-4-deoxy-) -D-glucopyranosyl fluoride (prepared from the corresponding a-D-glucopyranosyl chloride by the AgF method ) avermectin B , using protected sugar derivatives of oleandrosyl fluoride (a-L-Ole-F) and 0-(a-L-01e)-(1 4)-a-L-0le-F (both... 

Fisera L (2007) 1,3-Dipolar Cycloadditions of Sugar-Derived Nitrones and their Utilization in Synthesis. 7 287-323... 

In 1999, these authors reported the synthesis of the first family of sugar-derivative dithioethers containing sulfur as a unique donor atom. These chiral Ci-symmetric dithioether ligands were tested in the iridium-catalysed... 

Holzapfel and coworkers [132] used the carbopalladation ofalkynes followed by a cyclization for the synthesis of tricyclic compounds as 6/1-280, derived from the sugar derivative 6/1-279 (Scheme 6/1.74). 

Giese has used this strategy for the synthesis of sugar derivatives, as shown in Eq. 7.82.129... 

A. P. Rauter, F. Ramoa-Ribeiro, A. C. Fernandes, and J. A. Figueiredo, A new method of acetonation with the zeolite HY as catalyst. Synthesis of O-isopro-pylidene sugar derivatives, Tetrahedron, 51 (1995) 6529-6540. 

V. K. Rajput and B. Mukhopadhyay, Sulfuric acid immobilized on silica An effcient reusable catalyst for the synthesis of O-isopropylidene sugar derivatives, Tetrahedron Lett., 47 (2006) 5939-5941. 

The favored oxidative cleavage of a primary-secondary over a primary-tertiary vicinal diol grouping has been utilized in the synthesis of branched-chain sugar derivatives.482,483... 

More recently, the synthesis of relatively stable chiral acyl nitronates by the reactions of acetic anhydride and pyridine with secondary nitro sugar derivatives has been documented (221). 

Kochetkov and coworkers have reported [154—156] an efficient approach for the synthesis of 1,2-cis pyranosides employing 1,2-trcms-glycosyl thiocyanates as glycosyl donors and tritylated sugar derivatives as glycosyl acceptors (Scheme 4.5). This... 

Porphyrinyl-type sugar derivatives synthesis and biological 199... 

However, this multistep procedure is experimentally complex. A simpler variation described in 199127 consists of the reaction of an aldehyde and a nitro compound in the presence of triethylamine, TBAF and tert-butyl-dimethylsilyl chloride. Under these conditions, nitro sugars are obtained in good yieds and higher diastereoselectivities than those afforded by the standard conditions. This procedure was used in several synthesis of 2-nitro-2-deoxyaldoses, as for the condensation of l,l-diethoxy-2-nitroethane and l,2 3,4-di-0-isopropylidene-a-D-galacto-hexodialdo-l,5-piranose.28 More recently, it was applied to the addition of ethyl nitroacetate to the D-glucose derived aldehyde 18, to give nitro sugar derivatives 26, key precursors of polysubstituted cyclohexane a-amino acids (Scheme 10).29... 

This report deals with the synthesis and biological evaluations concerning photodynamic therapy properties of porphyrinyl- and dihydroporphyrinyl-type sugar derivatives. The chosen conjugates have O- and >S-glycosidic moieties or ether and ester functions. 

The synthesis shown in Fig. 40 provided access to heptoses,55 but according to our definition, this is not a higher sugar synthesis. However, the approach to such derivative was based on the Baylis-Hillman reaction of acyclic sugar-derived aldehydes, a reaction not commonly applied in sugar chemistry and worth to mention in this review. 

---