Research on Asymmetric Autocatalysis, Chiral Recognition and Origin of Chirality

在嘧啶-5-乙醛与二异丙基锌的反应中，嘧啶烷醇具有不对称自催化作用，生成了高度富集对映体的嘧啶烷醇，且具有相同的结构和绝对构型。当使用对映体过量（ee）非常低的不对称自催化剂时，可以观察到ee的显著扩增。从极低ee的不对称自催化开始，连续三次不对称自催化得到了几乎对映纯的（约99.5% ee）嘧啶烷基醇。不对称自催化作用被用来检验手性起源的有效性。发现氯酸钠等手性无机晶体是不对称自催化的手性引发剂。圆偏振光（CPL）直接照射外消旋嘧啶烷醇并进行不对称自催化反应，得到与CPL方向相关构型的高度对映富集的嘧啶烷醇。此外，CPL通过不对称光平衡诱导对映富集的某些酮烯可作为不对称自催化反应的手性引发剂。胞嘧啶等非手性有机化合物的手性晶体是不对称自催化的手性引发剂。在不添加手性引发剂的情况下，嘧啶-5-乙醛与二异丙基锌在无手性硅胶存在下进行了自然绝对不对称合成。采用不对称自催化技术对饱和季烃等隐手性化合物进行了手性判别。如上所述，我们发现了具有对映体富集扩增的高效不对称自催化，并应用该反应来阐明手性和手性鉴别的起源。

Pyrimidyl alkanol was found to act as an asymmetric autocatalysis in the reaction between pirimidine-5-carbaldehyde and diisopropylzinc, affording highly enantioenriched pyrimidyl alkanol with the same structure and absolute configuration. When asymmetric autocatalyst with very low enantiomeric excess (ee) was employed, significant amplification of ee was observed. Starting from asymmetric autocatalyst with very low ee, three consecutive asymmetric autocatalysis afforded practically enantiopure (>99.5% ee) pyrimidyl alkanol. Asymmetric autocatalysis has been employed to examine the validity of the origin of chirality. It was found that chiral inorganic crystal such as sodium chlorate act as chiral initiator of asymmetric autocatalysis. Direct irradiation of circularly polarized light (CPL) to racemic pyrimidyl alkanol and the subsequent asymmetric autocatalysis gave highly enantioenriched pyrimidyl alkanol with the related configuration to that of the direction of CPL. In addition, certain ketoolefin to which CPL induces the enantioenrichment by asymmetric photoequilibrium can act as a chiral initiator of asymmetric autocatalysis. Chiral crystals of achiral organic compound such as cytosine acts as chiral initiator of asymmetric autocatalysis. Spontaneous absolute asymmetric synthesis in the presence of achiral silica gel was achieved without adding chiral initiator in the reaction between pyrimidine-5-carbaldehyde and diisopropylzinc. Chiral discrimination of cryprochiral compound such as satirated quaternary hydrocarbon was achieved by using asymmetric autocatalysis. As described, we have found highly efficient asymmetric autocatalysis with amplification of enantioenrichment and applied the reaction to elucidate the origin of chirality and chiral discrimination.