Carba-disaccharides synthesis

In order to develop potent D-glucosidase inhibitors, a synthesis of carba-disaccharides containing valiolamine (205) was attempted by Horii and his coworkers utilizing method c. Coupling 205 with the 4-ketose 403, using NaBHjCN and hydrochloric acid, was effective in DMF, giving, after deprotection, the epimeric carba-disaccharides (404 and 405). The saturated... 

Such carba-disaccharides as validoxylamines A and B were synthesized as intermediary compounds in the total synthesis of validamycin antibiotics. Carba-disaccharides related to maltose, isomaltose, cellobiose, the trehaloses, and trehalosamine modifications have also been synthesized. 

SCHEME 8.16 Synthesis of a carba-disaccharide using a carbocationic cyclization. 

As previously stated, a distinct feature of this rearrangement is the retention of the anomeric information. This advantage is nicely illustrated by the direct synthesis of a carba-disaccharide from a disaccharide [65]. As shown in Scheme 8.35, maltose was first transformed into the thioglycoside 131. Manipulation to the free primary alcohol 132 was achieved using a classical sequence of reactions. At this point, glycosylation of methanol was realized in the presence of NCS to afford 133, and the unsaturated derivative 134 was obtained after iodination and elimination. Triisobutylaluminum induced rearrangement nicely afforded the carba-disaccharide precursor 135 in a yield of 89% as a mixture of two isomers. 

The synthesis of the carba di- and tri-saccharides 103 has been described. and the preparation of carba-disaccharide 104 by a similar process to that reported earlier (Vol. 25, p. 214, ref. 95) has appeared. For the preparation of glycosides of cyclitol derivatives see also Chapter 3. Carbocyclic analogues of GDP fucose have been made as potential inhibitors of fucosyl transferases. ... 

The carba-disaccharide 81 has been designed as an antigen for preparing glycoside-bond forming catalytic antibodies with catalytic groups. In its synthesis the addition of an acetylide anion to a carbocyclic ketone, followed by an OH Ns replacement, formed the key steps. 

In the area of carba-disaccharides, the synthesis of dicarba-a,a-trehalose, togedier widi the analogues 110a and 111 have been reported as potential trehalase inhibition. ... 

Analogues of complex saccharides, in which one or other of the acetal oxygens is replaced by a methylene residue or other heteroatoms, have received attention as biochemical probes and as potential therapeutic agents. The use of l-thio-1,2-isopropylidene acetals (TIA s) as annulating synthons for highly hydroxylated systems is illustrated by the synthesis of (3-C-, p-aza-C- and P-carba- galacto disaccharides. 

X. Cheng, N. Khan, G. Kumran, and G. Mootoo, A convergent strategy for the synthesis of 3-carba-galacto-disaccharides, Org. Lett., 3 (2001) 1323-1326. 

The synthesis of pseudo-disaccharides such as laminarabinose (78) by coupling the known Carbohydr. Res., 1985,136, 77) 5a-carba-l,2 4,6-di-0-isopropylidene laminarabinose-a or p-D,L-gIucopyranose with 2,3,4,6-tetra-O-acetyl-a-D-... 

The a- and /8lithium exchange. C-GlycosUated aminoacids were obtained by reaction of intermediate 23 with lactams [14], meanwhile the reaction of compounds 24 and 25 with electrophiles led to a- and -C-galactosides [22], respectively, intermediate 26 being used in the stereocontroDed synthesis of carba-C-disaccharides [23]. 

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