Total synthesis of scutellarin and apigenin 7-O-β-d-glucuronide

Synthetic Investigation toward QS-21 Analogues

“…As in the case of donor 1a , the condensation yield was eventually improved to 80% by elevating the reaction temperature to 65 °C and increasing the amount of catalyst to 0.3 equiv (entry 9). Finally, the reaction of glucuronyl ABz donor 1j with 2 was examined since a glucuronyl moiety constitutes the core sugar of the left-wing trisaccharide of QS-21 and its analogues. Pleasantly, when the glycosylation between 2 and inert donor 1j was carried out under the standard conditions, the glycosylation product 3j was isolated in a respectable 75% yield (entry 10), verifying the robustness of the established protocol.…”

Oxidation of Iodine to Dihaloiodate(I) Salts of Amines With Hydrogen Peroxides and Their Crystal Structures

“…Benzyltrimethylammonium DCI (PhCH 2 Me 3 N + ICl 2 − ) was prepared and used for the iodination of aromatic amines ( Kajigaeshi et al, 1988a ), fenols ( Kajigaeshi et al, 1987 ), aromatic ethers ( Kajigaeshi et al, 1988b ), acetanilides ( Kajigaeshi et al, 1989 ) and even as a catalyst in the four-component synthesis of pyrroles ( Pagadala and Kusampally, 2019 ). Recently, it was also used in the total synthesis of scutellarin ( Liu et al, 2019 ), an enantioselective synthesis of islatravir ( Patel et al, 2020 ) and secalonic acid ( Qin and Porco, 2014 ). Polymer-bound DCI compounds have also been developed ( Šket et al, 1989 ; Sumi Mitra and Sreekumar, 1997 ; Bahrami-Nasab and Pourali, 2014 ).…”

Total Syntheses of Aturanosides A and B

“…First, we examined the Mitsunobu glycosylation, which has been found to be particularly useful for the glycosylation of phenols; however, the reaction of 10b and lactol 15 did not take place under the conventional Mitsunobu conditions (entries 1 and 2). The gold­(I)-catalyzed glycosylation with o -alkynylbenzoate donors (e.g., 16 ) has been successfully applied to the glycosylation of a wide variety of nucleophiles, including electron-deficient phenols. , Unfortunately, the glycosylation of 10b with donor 16 proceeded sluggishly in the presence of PPh 3 AuNTf 2 (entry 3), leading to coupled α-rhamnoside 20 in only 42% yield even with heating (1 equiv of PPh 3 AuNTf 2 , CH 2 Cl 2 , 45 °C; entry 4). This result testified to the poor nucleophilicity of anthraquinone phenol 10b , resulting in decomposition of the donor before glycosylation.…”