Abstract
The $^1H$ NMR chemical shifts and coupling constants for ${\alpha}$-, permethyl-${\alpha}$-, ${\beta}$-and permethyl-${\beta}$-cyclodextrins in neutral aqueous media were assigned based on the 470MHz spectra. In order to obtain accurate chemical shifts and coupling constants the experimental spectra were analyzed with the Raccoon spin simulation program. The rotamer distribution around the$C_{5-}C_6$ bond of the cyclodextrins evaluated from the coupling constants of $J_{56a}$ and $J_{56b}$. In our calculation of the ${\alpha}$-, and ${\beta}$-cycliodextrin showed that gg conformers were most favorable form and tg conformers were least favorable form. It is very interesting to note the changes in $J_{56a}$, $J_{56b}$ coupling constants of permethylated ${\alpha}$- and ${\beta}$-cyclodextrins from unmodified one. The gg conformers were more increased than unmodified one and instead of tg conformers gt conformers were least favorable one upon methylation.
${\alpha}$-와 ${\beta}$-시클로덱스트린과 그의 메틸유도체들을 Chemical shift(${\delta}$)와 Coupling constant(J)를 470 MHz $^1H$ NMR을 이용해서 수용액 안에서 분석하였다. 정확한 ${\delta}$와 J값들을 얻기 위해서 Raccoon spin simulation program을 이용해서 실험 data를 분석하였다. 시클로덱스트린의 $C_{5-}C_6$ bond 주위의 rotamer의 분포를 $J_{56a}$ 와$J_{56b}$값을 이용하여 실험 data를 분석하였다. 위 계산에 의해 ${\alpha}$-와 ${\beta}$-시클로덱스트린에서는 gg conformer가 가장 많이 존재하였고 tg conformer가 가장 적게 존재했다. 그러나 그 메틸 유도체에서는 gg conformer가 더 많이 증가하였고 gt conformer가 가장 적게 존재함을 알았다.