Open-chain sugar

The addition of (Z)-3-(alkylamino)-2-butenoic acid esters to nitroalkenes derived from open-chain sugars gave a 50 50 mixture of diastereomeric products 32. The reaction of chiral 2-sub-stituted l-(2-nitroethenyl)pyrrolidines with zinc enolates of 3-substituted tetrahydro-2//-pyran-2-oncs in 1,2-dimethoxyethane at — 78 °C afforded the corresponding 3,3-disubstituted products in 82-96% ee via an addition-elimination process33. The stereochemical course of the reaction was determined by chemical correlation of (S)-( )-3-ethyltetrahydro-3-(2-ni-troethenyl)-2//-pyran-2-one with ( + )-quebrachamine. 

For examples of open-chain sugar-based diphosphanes (a) M. Yamashita,... 

Condensation of D-glucono-1,5-lactone with 4 5-diamino-6-diethyla-mino-2-methylpyrimidine afforded the 8-polyhydroxyalkylpurine 101, a C-nucleoside of an open-chain sugar (118). Some other pyrimidines gave analogous products from either D-glucono- or D-ribono-lactones. 

In an APTT clotting assay, which reflects not only the AT III - mediated events but also HC II and other factors of the coagulation cascade besides thrombin and factor Xa, sulfated spaced open chain sugars reached selectivities against... 

Table 3. Activities of sulfated spaced open chain sugars ...

An open-chain sugar has been alkynylated with 1,2-syn selectivity, using acetylides ( ) in the presence of zinc(II) chloride.216... 

The most important compounds from this class are undoubtedly 3,6-anhydrofuranoses. Fura-nodictine A and B (produced by cellular slime mold Dictyostelium discoideum) showing neuronal differentiation activity [54] are good examples. These interesting derivatives may be conveniently obtained from the open-chain sugars. For example, synthesis of furanodictine A was realized from compound 85 obtained from D-arabinose in a few well-defined steps as shown inO Fig. 19 [55]. 

Generally two main classes of unsaturated sugars in which (1) the anomeric carbon atom is involved in a double bond (glycals) and (2) the unsaturation is placed between other carbon atoms are known. One has to discuss also derivatives with the exo- and enclo-unsaturated bonds (either oleflns/dienes or acetylenes). Another class of unsaturated monosaccharides is represented by the open-chain sugars with the double bond(s) and/or triple bond present in the molecule. The examples of different types of unsaturated sugars are shown in O Fig. 2. Compounds such as glycals will not be discussed here, unless they are used as substrates for the preparation of other, non-anomeric, unsaturated derivatives. 

One of the first unsaturated open-chain sugars (observed for the first time by Emil Fischer) was obtained by hydrolysis of tri-O-acetyl-D-glucal (23). Heating of this compound in water results in smooth formation of the E-a./S-unsaturated open-chain aldose 76 (O Scheme 34) [1]. The carbonyl group can be protected, which allows one to replace the acetate blocks into more stable benzyl groupings thus providing compound 77 (O Scheme 34) [71],... 

Synthesis of unsaturated open chain sugars by fragmentation reactions... 

Carboranes are particular cyclic spacers that have been introduced for boron neutron capture therapy to be taken up by tumor cells [295,296,297]. Aromatic spacers have been integrated in cyclodextrin analogues to modify the guest binding properties [298,299,300]. Also amide-linked polymeric open chain sugars with aromatic spacers were prepared [257,264,301]. Sugars with cyclic spacers are also found in Nature [302], well known examples are antibiotics such as calicheamicin [303,304] or vancomicin [305]. 

The efficiency of this method is impressively proved by the synthesis of the skeleton of shikimic and chinic acid starting from an open chain sugar derivative and the synthesis of optically active cyclopent-anediol synthetic building blocks from tartaric acid. ... 

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