title: Unexpectedly convenient and stereoselective synthesis of 4α-acyloxy-2-chloropodophyllotoxins in the presence of BF₃ ·Et₂O.
abstract: Twenty-one 4α-acyloxy-2-chloropodophyllotoxin derivatives (5a-u), whose C-4 spatial configuration was mainly stereocontrolled by the configuration of C-2 chlorine atom, were unexpectedly prepared by the reaction of 2-chloropodophyllotoxin with carboxylic acids in the presence of BF(3)·Et(2)O. Compared with ordinary esterifications of carboxylic acids mediated by the condensation agent, for example, N,N'-diisopropylcarbodiimide (DIC), the present method made the procedure for the preparation of 4α-acyloxy-2-chloropodophyllotoxins more convenient, practical and easy. Meanwhile, the insecticidal activity of compounds 5a-u was preliminarily evaluated against the pre-third-instar larvae of Mythimna separata Walker in vivo at the concentration of 1mg/mL.
authors.affiliation: Laboratory of Pharmaceutical Design and Synthesis, College of Sciences, Northwest A&F University, Yangling 712100, China. orgxuhui@nwsuaf.edu.cn
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.forename: Xiao
authors.initials: X
authors.lastname: Xiao
authors.forename: Xue-Fei
authors.initials: XF
authors.lastname: Zhao
authors.forename: Yong
authors.initials: Y
authors.lastname: Guo
authors.forename: Xiao-Jun
authors.initials: XJ
authors.lastname: Yao
mesh_terms: D000215:Acylation; D000818:Animals; D001880:Boranes / Q000737:chemistry*; D002713:Chlorine / Q000737:chemistry*; D007306:Insecticides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D007814:Larva / Q000187:drug effects*; D015394:Molecular Structure; D009036:Moths; D011034:Podophyllotoxin / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013237:Stereoisomerism; D013997:Time Factors
chemical_list: D001880:Boranes; D007306:Insecticides; C101707:boron trifluoride etherate; D002713:Chlorine; D011034:Podophyllotoxin