Asymmetric Autocatalysis as a Link Between Crystal Chirality and Highly Enantioenriched Organic Compounds

Abstract

The origin of biological homochirality has attracted much attention. Pyrimidyl alkanols exhibit asymmetric autocatalysis with significant amplification of enantiomeric excess in the reaction between pyrimidine-5-carbaldehyde and diisopropyl zinc (the Soai reaction). Chiral inorganic crystals such as quartz, cinnabar and sodium chlorate act as chiral triggers of asymmetric autocatalysis to afford highly enantioenriched pyrimidyl alkanol, with the absolute configurations corresponding to those of the chiral crystals. Chiral organic crystals composed of achiral organic compounds such as cytosine, adenine dinitrate, and γ-glycine act as the chiral triggers of the Soai reaction to afford pyrimidyl alkanol with high ee that corresponds to the absolute configuration of the chiral trigger. This review describes that chiral minerals and chiral organic crystals act as the chiral triggers of the Soai reaction and that these chiral crystals are correlated to near-enantiopure chiral organic compounds.

Chirality in Organic and Mineral Systems: A Review of Reactivity and Alteration Processes Relevant to Prebiotic Chemistry and Life Detection Missions

“…One of the most notable autocatalytic reactions in organic synthesis is the Soai reaction (Table 1), which produces a near enantiopure solution (>99.5% ee) in high yields (>99%) using 3-pyridylalkanol as an asymmetric autocatalyst [26]. As summarized in the review by [212], the organic autocatalyst of the Soai reaction can be successfully substituted for more prebiotically relevant catalysts, including the minerals quartz, gypsum, retgersite, cinnabar, sodium chlorate, and sodium borate-all of which generated near enantiopure solutions in high yields [27,[213][214][215][216][217]. These results demonstrate how minerals can induce significant enantioselectivity when subjected to asymmetric autocatalytic reactions.…”

Achiral 2‐pyridone and 4‐aminopyridine act as chiral inducers of asymmetric autocatalysis with amplification of enantiomeric excess via the formation of chiral crystals

“…[48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63] We have also reported that a chiral crystal of achiral organic compounds could act as a heterogeneous chiral trigger for asymmetric autocatalysis. 64,65 Unlike using chiral crystals as a substrate for stereospecific reactions, a large amount of highly enantioenriched compounds can be synthesized from a catalytic amount of initial chiral crystals in conjunction with asymmetric autocatalysis. [66][67][68][69] Here, we demonstrate the highly enantioselective synthesis of 5-pyrimidyl alkanol 2 induced by enantiomorphous crystals of achiral 2-pyridone 3 and 4-aminopyridine 4 in conjunction with asymmetric autocatalysis (Figure 1).…”

“…We have also reported that a chiral crystal of achiral organic compounds could act as a heterogeneous chiral trigger for asymmetric autocatalysis 64,65 . Unlike using chiral crystals as a substrate for stereospecific reactions, a large amount of highly enantioenriched compounds can be synthesized from a catalytic amount of initial chiral crystals in conjunction with asymmetric autocatalysis 66–69 …”

Possibility of chiral recognition by adsorption on enantiomorphous crystals: the impact of crystal surface polarity

“…Subsequently, Soai's group performed an indepth study of the potential of enantiomorphic crystals for the asymmetric catalysis of the pyrimidine-5-carbaldehyde/diisopropylzinc reaction. [14][15][16] As a result, it was shown that many enantiomorphic crystals, both polar (cytosine, 17 retgersite, 18 quartz, 19 etc.) and weakly polar (tetraphenylethylene 20 and benzyl 21 ), are capable of catalysing the pyrimidine-5-carbaldehyde and diisopropylzinc reaction.…”