345197-66-2

Upstream product

• 108-98-5 thiophenol 
• 4098-06-0 triacetyl-D-galactal 
• 125654-34-4 (2R,3R,6R)-2-Hydroxymethyl-6-phenylsulfanyl-3,6-dihydro-2H-pyran-3-ol 
• 77-76-9 2,2-dimethoxy-propane 
• 125848-19-3 phenyl-2,4-di-O-acetyl-2,3-dideoxy-1-thio-α-D-threo-hex-2-eno-pyranoside 
• 116-11-0 2-Methoxypropene 

Relevant academic research and scientific papers

Glycal Metallanitrenes for 2-Amino Sugar Synthesis: Amidoglycosylation of Gulal-, Allal-, Glucal-, and Galactal 3-Carbamates

The rhodium(II)-catalyzed oxidative cyclization of glycal 3-carbamates with in situ incorporation of an alcohol nucleophile at the anomeric position provides access to a range of 2-amino sugars having 1,2-trans-2,3-cis stereochemistry, a structural motif present in compounds of medicinal and biological significance such as the streptothricin group of antibiotics and the Chitinase inhibitor allosamidin. All of the diastereomeric d-glycal 3-carbamates have been investigated, revealing significant differences in anomeric stereoselectivity depending on substrate stereochemistry and protecting groups. In addition, some substrates were prone to forming C3-oxidized dihydropyranone byproducts under the reaction conditions. Allal- and gulal 3-carbamates provided uniformly high stereo- and chemoselectivity, while for glucal substrates, acyclic, electron-withdrawing protecting groups at the 4O and 6O positions were required. Galactal 3-carbamates have been the most challenging substrates; formation of their amidoglycosylation products is most effective with an electron-withdrawing 6O-Ts substituent and a sterically demanding 4O-TBS group. These results suggest a mechanism whereby conformational and electronic factors determine the partitioning of an intermediate acyl nitrenoid between alkene addition, leading to amidoglycosylation, and C3-H insertion, providing the dihydropyranone byproduct. Along the amidoglycosylation pathway, high anomeric selectivity results when a glycosyl aziridine intermediate is favored over an aziridine-opened oxocarbenium donor.

Organotransition metal modified sugars: Part 22. Direct metalation of glycals: Short and efficient routes to diversely protected stannylated glycals

A complete set of D-hexose-derived silyl and isopropylidene/silyl-protected glycals bearing complementary configurations at C-3 and C-4 has been synthesized in short and efficient 1-3 step sequences from standard precursors. The glycals have been applied to metalation reactions to give storable vinyl lithium equivalents by subsequent transmetalation to vinyl stannanes which represent valuable intermediates for transition metal-catalyzed cross-coupling reactions. A 1H-NMR-assisted conformational analysis has been carried out with the protected glycals and the stannylated congeners. The isopropylidene/silyl-protected glycals adopt the 4H5-conformation caused by the bicyclic system, whereas the conformations of the fully silyl-protected monocyclic glycals are mainly controlled by the vinylogous anomeric effect. The discussed galactal- and allal-derivatives show dynamic behaviour on the NMR-time-scale. At low temperatures the two possible conformers (4H5 and 5H4) have been observed demonstrating competition of steric congestion and stereoelectronic interaction via the vinylogous anomeric effect (VAE).