Macrocyclic glycosides

Good -selectivity (a as high as 1 16) was found on reaction of 4-Q-acetyl-6-deoxy-2,3-di-Q-methyl-/9-D-allopyranosyl fluoride (D-mycinosyl fluoride) with alcohols in the presence of silver perchlorate and bis(cyclopentadienyl)zirconium dichloride in benzene,and in related fashion a desosamine fluoride has been used to produce -glycosides under mild conditions involving a hafnium complex and the methods have been combined in a total synthesis of the macrocyclic glycoside mycinamycin IV. 

Scheme 45 Macrocyclization by RCM in Fiirstner s total synthesis of the resin glycoside woodrosin I (218) [104]...

The direct comparison of 1 and 2 in a variety of RCM reactions also indicates a presumably close relationship between these catalysts (Table 1) [6]. Both of them give ready access to cycloalkenes of almost any ring size > 5, including medium sized and macrocyclic products. Only in the case of the 10-membered jasmine ketolactone 16 was the yield obtained with 2a lower than that with lc this result may be due to a somewhat shorter lifetime of the cationic species in solution. However, the examples summarized in Table 1 demonstrate that the allenylidene species 2 exhibit a remarkable compatibility with polar functional groups in the substrates, including ethers, esters, amides, sulfonamides, ketones, acetals, glycosides and even free hydroxyl groups. 

Finally, macrocyclization is carried out via protection and deprotection sequences and cyclization of the activated ester 26, and this accomplishes the synthesis of 27 (Scheme 7-6), which, through deprotection and glycosidation, can be converted to erythromycin A, a compound containing a hopelessly complex array of chiral centers.4... 

This review deals with the synthesis of porphyrinyl-type sugar conjugates developed and biologically accessed, and considers the involvement of macrocycles of the porphyrin and chlorin (dihydroporphyrin) types, with O- and 5-glycosides or ether and ester functions. 

Scammonin VIII (104), isolated from Convulvulus scammonia, is a linear tetra-saccharide of jalapinolic acid with two glucoses, one rhamnose, and one quinovose. This compound represents the only macrocyclic resin glycoside of scammonic acid B (hexadecanoic acid, (115)-[(0-jS-D-glucopyranosyl-(l—>4)-0-6-deoxy-a-L-man-nopyranosyl-(1 2)-0- S-D-glucopyranosyl-(l- 2)-6-deoxy- S-D-glucopyranosyl)oxy]). 

They contain 12-, 14-, or 16-membered macrocyclic lactone rings attached to amino acids and/or a neutral sugar moiety attached via glycoside bonds. Beyond this, their individual chemical structures and sizes as reflected by molecular weight are dramatically different. Thus, despite exerting similar mechanisms on bacteria, they are very chemically different from each other. 

However, directionality of individual non-covalent interactions is not always needed and even non-directional forces such as the hydrophobic effect can be utilized for the preparation of interlocked structures. Cyclodextrins may serve as a first example. They are macrocycles built from a-glycosidic D-glucose subunits. While their hydrophilic, OH group-decorated surface makes them water soluble, they bear a lipophilic... 

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