Glycosidation selectivity

Cham et al., "Solasodine glycosides. Selective toxicity for cancer cells and inhibition of cytotoxicity by rhamnose in mice with sarcoma 180." Cancer Letters (1990). 55(3) 221-225. 

An important question remains why do cardiac glycosides selectively affect the heart although they are distributed from the bloodstream to the kidneys and liver, organs rich in ATPase ... 

Cardiac Glycosides Selectively Inhibiting Tumor Cells... 

It was of interest to determine whether glycosides of 6-deoxy-D-xylo-hex-5-enopyranose were susceptible to enzyme hydrolysis by / -glucosi-dase. Since aromatic glucosides are hydrolyzed by this enzyme at a much faster rate than aliphatic glycosides, phenyl 6-deoxy-/ -D-rt/Zo-hex-5-enopyranoside (18) was prepared (20). Phenyl / -D-glucopyranoside was converted to the 6-tosylate by selective esterification and then, by conventional procedures, transformed to phenyl 2,3,4-tri-0-acetyl-6-deoxy-... 

The present work involves the study of methyl glycosides and O-isopropylidene ketals of various isomeric deoxy sugars by mass spectrometry. Several of the compounds selected for the present study have free hydroxyl groups, and interpretation of their mass spectra shows the scope of the study of these and related deoxy sugar derivatives by mass spectrometry without prior substitution of all hydroxyl groups. Some of the candidates (compounds 4, 7, 8 and 10) are structurally related to biologically-derived deoxy sugars. 

If it is assumed that the Mitsunobu glycosidation reaction described above proceeds through an SN2-type process with inversion of configuration at the anomeric position, then it follows that the desired / -glycoside can be formed selectively if pure a-lactol 17 is used in the reaction. Unfortunately, the /Mactol isomer of 17 is thermodynamically more stable than the a-diastereoisomer and is formed almost exclusively if the system is allowed to fully equilibrate. In the protic medium used for the Luche reduction, a signifi-... 

Anew route to 2,5-dihydrofiirans and tetrahydro[3,2-b]furans via ring contraction of pyranoside C-glycosides was reported <96CC1663>. ( )-Homononactic acid and its 8-epimer were synthesized by using a c -selective iodoetherification as the key step (Scheme 21, <96SL777>). 

Fig. 6 Highly 3-selective glycosidation to couple the C-2 branched furanose epoxide with the 7-deazapurine...

Beau and Sinay described a method which laid the groundwork for cyanohydrin acetonide alkylations [1]. Their strategy involved alkylation and reductive desulfonylation of glucopyranosyl sulfones 4. In this one-pot procedure, low temperature alkylation and subsequent reductive desulfonylation with lithium naphthalenide generated -C-glycosides with good selectivity >10 1 j3 a) and in moderate to good yield (Eq. 1). 

---