Phytotoxins from Hofmeisteria schaffneri:Isolation and Synthesis of 2'-(2'-Hydroxy-4'-methylphenyl)-2'-oxoethyl Acetate

摘要

Activity-directed fractionation of a CH_2Cl_2-MeOH (1:1) extract of Hofmeisteria schaffneri led to the isolation of a new phytotoxin characterized as 2'-(2"-hydroxy-4"-methylphenyl)-2'-oxoethyl acetate and designated the trivial name of hofmeisterin (1).In addition,the known compounds beta-carotene,euparin,and 3',4',4a',9a'-tetrahydro-6,7'-dimethylspiro[benzofuran-3(2H),2'-pyrano[2,3-6]benzofuran]-2,4a'-diol(2) were obtained.The identification of the isolates was accomplished by spectroscopic methods.The structure of 1 was unequivocally confirmed by synthesis.The methyl derivative la was also synthesized following the same strategy.Compounds 1 and 2 inhibited radicle growth of Amaranthus hypochondriacus (IC_(50)=3.2 x 10~(-4) and 1.2 x 10~(-5) M,respectively) and significantly inhibited activation of the calmodulin (CaM)-dependent enzyme cAMP phosphodiesterase (PDE) with IC_(50) values of 4.4 and 4.22muM,respectively.