Diastereodifferentiating Photocyclodimerization of 2-Anthracenecarboxylates Tethered to a Cyclic Tetrasaccharide Scaffold: Critical Control of Photoreactivity and Stereoselectivity

作者：Fukuhara Gaku^*; Nakamura Tomohiro; Kawanami Yuko; Yang Cheng; Mori Tadashi; Hiramatsu Hiroyuki; Dan oh Yasufumi; Nishimoto Tomoyuki; Tsujimoto Kazuo; Inoue Yoshihisa

来源：Journal of Organic Chemistry, 2013, 78(21): 10996-11006.

DOI：10.1021/jo401977f

From a complex mixture of mono- and di-2-anthracenecarboxylic acid (AC) esters of cyclic nigerosylnigerose (CNN), two monoesters (2(B)) and 6(A)) and four diesters in which AC was introduced on the transannular B/D (2(B)2(D)), adjacent A/B and A/D (6(A)2(B) and 6(A)2(D)), and same B/B (2(B)3(B)) nigerose rings were isolated. Possessing two ACs at distant positions, 2(B)2(D) and 6(A)2(D)) showed negative Cotton effects for the B-1(b) band, the intensities of which were stronger than that of 6(A). 2(B)2(D) and 6(A)2(D) slowly photocyclodimerized to give HH dimers 3* and 4 with 57% and 81% HH selectivity, respectively, which were appreciably higher than that for 6(A) (34%), while the enantiomeric excesses (ee's) of anti-HH dimer 3* were 2% and -18%, respectively. In contrast, 6(A)2(B) and 2(B)3(B) carrying two ACs on adjacent A and B rings or at vicinal positions on the B ring, respectively, exhibited strong positive CD couplets, the amplitudes of which amounted to 97 and 409 M-1 cm(-1), respectively. Upon irradiation, 6(A)2(B) afforded 3* with -62% ee and 4 in 96% combined yield, whereas 2(B)3(B) gave almost exclusively 3* with -99% ee in 96% yield, likely as a result of the introduction of two ACs at the vicinal positions of the rigid CNN scaffold.

• 出版日期2013-11-1