Short, Enantioselective Total Synthesis of Aflatoxin B₂ Using an Asymmetric [3+2]-Cycloaddition Step

A highly enantioselective [3+2]-cycloaddition reaction of 2,3-dihydrofuran with 1,4-benzoquinones using a chiral oxazaborolidinium triflimidate as catalyst has been developed which allows rapid access to a variety of chiral phenolic tricycles (enantiomeric excesses ranging from 91 to 98%). The utility of this new methodology is demonstrated by a short synthesis of the important pentacyclic natural product, aflatoxin B2. This exploratory study indicates that an even broader application of these catalysts to enantioselective cycloadditions may be possible.本研究开发了一种以手性恶唑硼鎓双(三氟甲磺酰基)亚胺盐为催化剂的高对映选择性[3+2]环加成反应，该反应以2,3-二氢呋喃与1,4-苯醌为反应物，可快速制备多种手性酚类三环化合物，产物对映体过量值介于91%至98%之间。该新型合成方法的应用价值通过重要五环天然产物黄曲霉毒素B2的简短合成路线得到验证。本探索性研究表明，此类催化剂在对映选择性环加成反应中的更广泛应用或成可能。