Synthesis of n-octyl 2,6-dideoxy-alpha-L-lyxo-hexopyranosyl-(1-->2)-3-amino-3-deoxy-beta-D-galactopyranoside, an analog of the H-disaccharide antigen.

The synthesis of an analog of the H-disaccharide antigen (2), in which the galactopyranosyl moiety bears an amino group at C-3 and the fucopyranosyl residue is deoxygenated at C-2, is reported. The key reaction in the preparation of 2 was the glycosylation of an appropriately protected n-octyl 3-azido-3-deoxy-galactopyranoside derivative with a 2,6-dideoxy thioglycoside promoted by 1-(phenylsulfinyl)piperidine and triflic anhydride. Disaccharide 2 is of interest in studies directed towards understanding the molecular basis of substrate recognition by the blood group A and B glycosyltransferases.

Synthesis of sterically hindered ortho-substituted tetraphenylethenes. Electronic effects in the McMurry olefination reaction.

[reaction: see text] Contrary to literature consensus, the McMurry olefination reaction can be extended to the direct synthesis of sterically encumbered tetrakis(2-substituted) tetraphenylethenes from the corresponding 2,2'-disubstituted benzophenones. The reaction exploits previously unrecognized substrate-based electronic effects that dominate over otherwise controlling steric considerations and provides highly efficient access to derivatives of tetrakis(2-hydroxyphenyl)ethene, a novel preorganized ligand system for polymetallic coordination chemistry and catalysis.

Selective syntheses of partially etherified derivatives of tetrakis(2-hydroxyphenyl)ethene. An alternative to the calix[4]arene ligand system.

Stereoselective syntheses of (E)- and (Z)-1,2-bis(2'-hydroxyphenyl)-bis(2'-methoxyphenyl)ethene have been developed, the former by convergent coupling of an orthogonally protected 2,2'-benzophenone derivative and the latter by selective partial dealkylation of tetrakis(2-methoxyphenyl)ethene. Selective single demethylation has also been demonstrated in the 5-tert-butyl series. Thus, divalent and monovalent derivatives of the preorganized tetrakis(2-hydroxyphenyl)ethene ligand system are now available for use in coordination chemistry, analogous to corresponding calix[4]arene systems.