Genus Caulophyllum: An Overview of Chemistry and Bioactivity

Scheme 4

(A) Design of ring-opened target compounds 𝟏𝟗^′--𝟐𝟒^′; (B) preparation of target compounds (𝟏𝟗^′--𝟐𝟒^′). Reagents and Conditions: (a) Fe, NaOAc, AcOH, Br₂, 81%; (b) BnCl, K₂CO₃, 95%; (c) NaH₂PO₄, NaClO₂, 30% H₂O₂, 93%; (d) SOCl₂, DMF(cat), CH₂Cl₂, 96%; (e) CH₂Cl₂, 30% CH₃NH₂, 85%; (f) Cu, DMF, 72%; (g) H₂, Pd/C; 97%; (h) K₂CO₃, DMF, (26, 64%; 25, 76%); (i) K₂CO₃, EtOH, (27, 72%; 28, 59%; 29, 54%) [18, 42–44].