Keck asymmetric allylation in natural product synthesis: applications and developments (2018-2026).

Following our 2017 comprehensive review, this update highlights the evolving and pivotal role of the Ti-BINOL-catalyzed Keck asymmetric allylation in modern total synthesis. Highly regarded for its operational simplicity and outstanding enantiocontrol, the methodology still represents a cornerstone for the synthesis of optically active homoallylic alcohols and the assembly of complex molecular architectures. Herein, we review its application as a key stereodefining step in the recent syntheses of several structurally diverse and biologically active targets including (+)-ineleganolide, (+)-sieboldine A, ieodomycin derivatives, latrunculin B, (-)-melearoride A, PF1163B, cryptorigidifoliol G, cryptoconcatone I, and antarlides A-F. Besides traditional applications, this review also covers recent methodological advances to improve reaction efficiency, including the implementation of modified ligand frameworks and optimized additive systems. We also discuss frontier approaches that extend the classical scope of the reaction, with particular emphasis on emerging three-component asymmetric Tsuji-Trost allylations using chiral aldehydes and dual palladium catalysis.