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

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• 作者：Gaku Fukuhara ; Tomohiro Nakamura ; Yuko Kawanami ; Cheng Yang ; Tadashi Mori ; Hiroyuki Hiramatsu ; Yasufumi Dan-oh ; Tomoyuki Nishimoto ; Kazuo Tsujimoto ; Yoshihisa Inoue
• 刊名：Journal of Organic Chemistry
• 出版年：2013
• 出版时间：November 1, 2013
• 年：2013
• 卷：78
• 期：21
• 页码：10996-11006
• 全文大小：544K
• 年卷期：v.78,no.21(November 1, 2013)
• ISSN：1520-6904

文摘

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^B2^D), adjacent A/B and A/D (6^A2^B and 6^A2^D), and same B/B (2^B3^B) nigerose rings were isolated. Possessing two ACs at distant positions, 2^B2^D and 6^A2^D showed negative Cotton effects for the ¹B_b band, the intensities of which were stronger than that of 6^A. 2^B2^D and 6^A2^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鈥檚) of anti-HH dimer 3* were 2% and 鈭?8%, respectively. In contrast, 6^A2^B and 2^B3^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^鈥? cm^鈥?, respectively. Upon irradiation, 6^A2^B afforded 3* with 鈭?2% ee and 4 in 96% combined yield, whereas 2^B3^B gave almost exclusively 3* with 鈭?9% ee in 96% yield, likely as a result of the introduction of two ACs at the vicinal positions of the rigid CNN scaffold.