Faculty of Advanced Life Science, Frontier Research Center for the Post-Genome Science and Technology, Hokkaido University, Kita 21, Nishi11, Sapporo 001-0021, Japan.
J Nat Prod. 2011 Apr 25;74(4):707-11. doi: 10.1021/np1007763. Epub 2011 Mar 7.
Sotolon (1) and maple furanone (2) are naturally occurring chiral furanones. These 5-substituted-2(5H)-furanones are industrially significant aroma compounds due to their characteristic organoleptic properties and extraordinarily low odor thresholds. Each enantiomer of 1 and 2 was successfully obtained by preparative enantioselective supercritical fluid chromatography. The absolute configuration of 1 was confirmed as (R)-(-)-1 and (S)-(+)-1 by adopting the vibrational circular dichroism (VCD) approach. The absolute configuration of 2, which has remained ambiguous since its discovery in 1957, was determined as (R)-(+)-2 and (S)-(-)-2 for the first time by the VCD technique. Surprisingly, the signs of the optical rotation of 2 are opposite of those of 1 regardless of their identical absolute configurations. This observation emphasizes the risk in absolute configurational assignments based on comparison of optical rotation signs of similar structures. Odor evaluation of the enantiomers of 2 revealed different odor intensities.
苏糖醇（1）和枫呋喃酮（2）是天然手性呋喃酮。这些 5-取代-2(5H)-呋喃酮由于其独特的感官特性和极低的气味阈值，是具有工业意义的香气化合物。1 和 2 的每个对映异构体都通过制备性对映选择性超临界流体色谱成功获得。通过振动圆二色性（VCD）方法，确定 1 的绝对构型为（R）-（-）-1 和（S）-（+）-1。自 1957 年发现以来，2 的绝对构型一直存在争议，首次通过 VCD 技术确定为（R）-（+）-2 和（S）-（-）-2。令人惊讶的是，尽管它们的绝对构型相同，但 2 的旋光值的符号与 1 的相反。这一观察结果强调了基于类似结构的旋光值比较进行绝对构型分配的风险。2 的对映异构体的气味评估显示出不同的气味强度。
