A Brief Review of Synthetic Strategies of α-Pyrone-Based Phloroglucinol Derivatives from Helichrysum spp. and Structure–Activity Insights

This review summarizes the synthesis and structural modification of α-pyrone-containing phloroglucinol derivatives from Helichrysum species. Synthetic routes to both natural products and synthetic analogues are covered, highlighting strategies ranging from β-keto ester cyclodehydration to multicomponent condensations. Key methods include aldehyde-mediated dimerization, fluoride-catalyzed heterodimerization, and acid-catalyzed cyclization to benzopyran frameworks. The reported approaches enabled access to diverse monopyrone, dipyrone, аrzanol-type, and cyclized analogues. Additionally, retrosynthetic analyses toward phloroglucinol–pyrone heterodimers are discussed, highlighting convergent synthetic strategies for future access to benzofurane-, chromene-, and chromane-based analogues. This review integrates published experimental data with newly generated in silico predictions.