TY - JOUR A1 - Yoshikiyo, Keisuke A1 - Matsui, Yoshihisa A1 - Yamamoto, Tatsuyuki T1 - Qualitative evaluation of regioselectivity in the formation of di- and tri-6-O-tritylates of α-cyclodextrin JF - Beilstein Journal of Organic Chemistry PY - 2015/// VL - 11 SP - 1530 EP - 1540 SN - 1860-5397 DO - 10.3762/bjoc.11.168 PB - Beilstein-Institut JA - Beilstein J. Org. Chem. UR - https://doi.org/10.3762/bjoc.11.168 KW - 1H and 13C NMR spectroscopy KW - quantitative analysis KW - regioselectivity KW - tritylation KW - ultra-fast liquid chromatography (UFLC) N2 - The quantitative analysis of reaction products showed that the reaction of 6A,6D-di-O-trityl-α-cyclodextrin (CD), AD-isomer, with trityl chloride in pyridine at 55 °C gave 6A,6B,6E-tri-O-trityl-α-CD, the amount of which was only 25% of that of simultaneously formed 6A,6B,6D-tri-O-trityl-α-CD. This indicates that the bulky trityl groups of glucopyranose-A and -D (Glu-A and -D, respectively) in the AD-isomer mainly retard the additional tritylation of the C(6)-OH of the adjacent glucopyranoses in a counter-clockwise direction (Glu-F and -C, respectively). 1H NMR spectra of the AD-isomer showed that the O(6)-H and C(6)-H signals of Glu-C and -F are shifted upfield due to the ring current of the trityl groups. Thus, it is concluded that the bulky trityl groups on Glu-A and Glu-D are oriented to Glu-F and Glu-C, respectively, and sterically retard additional tritylation on Glu-F and Glu-C. Similar steric hindrance was also observed in the additional tritylations of mono-6-O-trityl-α-CD, 6A,6B-di- and 6A,6C-di-O-trityl-α-CD’s. ER -