Aryl-β-C-glucosidation using glucal boronate: application to the synthesis of tri-O-methylnorbergenin

Cross‐Coupling Reaction of Saccharide‐Based Alkenyl Boronic Acids with Aryl Halides: The Synthesis of Bergenin

“…Attempts to protect the boronic acid function of 4 a with pinacol under published conditions6 to obtain tri‐TIPS glucal pinacol boronate 4 b were not successful and resulted in the formation of complex reaction mixtures. Interestingly, its formation in high yield was claimed,7 but its spectral characterization was not reported. In view of the aforementioned results, we decided to approach the synthesis of TIPS‐protected glucal boronate 4 b by other means (Scheme ).…”

“…One approach to C ‐arylglycosides is based on the use of the corresponding 1‐alkenylboronic acids or their pinacol esters in the Suzuki–Miyaura cross‐coupling reaction6 with suitable substituted aryl and heteroaryl halides, and with alkenyl halides. During the course of our work on that subject, a report on a synthetic procedure for the synthesis of C ‐arylglycosides based on cross‐coupling reaction of glucal boronate with aryl(heteroaryl) bromides was published 7. The report clearly demonstrated the advantages of this approach; however, the scope of this investigation was limited to just six examples.…”

Glycoconjugated Phthalocyanines as Photosensitizers for PDT – Overcoming Aggregation in Solution

“…The starting material was reisolated under various conditions tested so far (hydrogenation with Pd/C in hexane, ethyl acetate, toluene, methanol and ethyl acetate, with Pt/C in ethanol and with Pd(OH) 2 in ethanol , BH 3 · SMe 2 ,, and 9‐BBN were also tested for hydroboration of the double bonds but did not react with 34 either. Obviously, the orientation of the silylgroups of the sugar moiety in 34 prevents hydrogenation.…”

Synthesis and Biological Evaluation of Thiophene-<i>C</i>-glucosides as Sodium-Dependent Glucose Cotransporter 2 Inhibitors

“…2, based on our reported reaction of aryl halide with glucal-boronate ester 4. 15) Coupling reaction using dichlorobis(triphenylphosphine) palladium (PdCl 2 (PPh 3 ) 2 ) between aglycons 7a-f and glucal-boronate 4 gave 5a-f, followed by stereoselective hydroboration and oxidation using H 2 O 2 in alkaline conditions yielded 6a-f with the desired β-configuration (J 1,2 ≈9.5 Hz). Finally, O-silyl groups of 6a-f were deprotected with tetra-n-butylammonium fluoride (TBAF) to afford thiophene-C-glucosides 3a-f. 16) Synthesis of thiophene aglycons 7a-f are shown in Fig.…”