Diterpenoids

Structural Characterization and Antimicrobial Evaluation of Atractyloside, Atractyligenin, and 15-Didehydroatractyligenin Methyl Ester

“…Previous attempts to prepare 3 from atractyligenin methyl ester were partially efficient. Direct oxidation of the latter with MnO 2 led to a mixture of 15-didehydro- ( 3 ) and 2,15-di(didehydro)-atractyligenin methyl ester ( 4 ) derivatives (Figure ) . A novel synthetic route for the preparation of 3 was developed, and selective oxidation of the C-15 hydroxy group was achieved utilizing the carbohydrate moiety of 1 as a protective group for the C-2 hydroxy group (Scheme ).…”

“…Direct oxidation of the latter with MnO 2 led to a mixture of 15-didehydro-(3) and 2,15-di(didehydro)-atractyligenin methyl ester (4) derivatives (Figure 1). 21 A novel synthetic route for the preparation of 3 was developed, and selective oxidation of the C-15 hydroxy group was achieved utilizing the carbohydrate moiety of 1 as a protective group for the C-2 hydroxy group (Scheme 1). Methylation of 1 at C-19 using (trimethylsilyl)diazomethane (TMSCH 2 N 2 ) gave atractyloside methyl ester 5.…”

“…More recently, some naturally occurring and semisynthetic tetracyclic ent -kaurane diterpenoids, structurally related to 1 and 2 , have attracted attention due to their interesting anticancer, antibacterial, and anti-inflammatory activity. − In particular, a semisynthetic derivative of atractyloside ( 1 ), 15-didehydroatractyligenin methyl ester ( 3 ), exhibited significantly higher cytotoxicity against selected cancer cell lines compared to 1 and 2 (Figure ) . This compound ( 3 ) contains in its molecular framework an exo -methylene group (C-16–C-17) conjugated with a carbonyl residue (C-15) and may exert its biological activity by acting as a Michael-type acceptor compound, with the α,β-unsaturated carbonyl system serving as the alkylating center …”