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Paper | Special issue | Vol 88, No. 2, 2014, pp.1121-1133
Published online, 26th August, 2013
DOI: 10.3987/COM-13-S(S)69
■ Rotational Energy Barrier around the C1–C11 Single Bond in Lamellarins: A Study by Variable-Temperature NMR

Tsutomu Fukuda, Ryosuke Itoyama, Terufusa Minagawa, and Masatomo Iwao*

*Division of Chemistry and Materials Science, Graduate School of Engineering, Nagasaki University, 1-14, Bunkyo-machi, Nagasaki 852-8521, Japan

Abstract

In order to estimate the free energy barrier to rotation around the C1–C11 single bond in lamellarins, new lamellarin analogues (1a), (1b), (2a), and (2b) possessing diastereotopic protons or carbons at the C1 aryl moiety were synthesized. Variable-temperature 1H and 13C NMR measurements of these analogues revealed that the free energy barriers to rotation around the C1–C11 axis in 5,6-saturated and 5,6-unsaturated lamellarins were around 72–74 and 83–87 kJ/mol, respectively.