Insight into 2α-Chloro-2′(2′,6′)-(Di)Halogenopicropodophyllotoxins Reacting with Carboxylic Acids Mediated by BF3·Et2O

Abstract

Stereospecific nucleophilic substitution at the C-4α position of 2α-chloro-2′(2′,6′)-(di)halogenopicropodophyllotoxin derivatives with carboxylic acids mediated by BF3·Et2O was described. Interestingly, this stereoselective products were completely controlled by the reaction time. That is, if the reaction time was prolonged to 24.5–31 h, the resulting compounds were all transformed into the unusual C-ring aromatization products. Additionally, it demonstrated that BF3·Et2O and reaction temperature were the important factors for C-ring aromatization, and AlCl3 could be substituted for BF3·Et2O as a lewis acid for C-ring aromatization. Halogenation of E-ring of 2β-chloropodophyllotoxins with NCS or NBS also led to the same C-ring aromatization compounds. Especially compounds 5c, 6g and 7b exhibited insecticidal activity equal to that of toosendanin.

Semisynthesis of novel N‐acyl/sulfonyl derivatives of 5(3,5)‐(di)halogenocytisines/cytisine and their pesticidal activities against Mythimna separata Walker, Tetranychus cinnabarinus Boisduval, and Sitobion avenae Fabricius

“…Among all derivatives, compound 7i exhibited insecticidal activity that was significantly different from that of toosendanin (FMR: 48.1%). Symptoms in treated M. separata during the larval, pupation and adult periods were the same as in our previous report . Figure shows dead larvae with thin and wrinkled bodies from the larval stage; Fig.…”

“…), 2α‐chloro‐4α‐acyloxy‐2′(2′,6′)‐(di)halogenopicropodophyllotoxins ( II , Fig. ), oxime sulfonates of 2′(2′,6′)‐(di)chloropicropodophyllotoxins ( III , Fig. ), and 2′‐chloro‐5‐bromo/2′,5‐dibromo‐4α‐acyloxypicropodophyllotoxins ( IV , Fig.…”

“…Symptoms in treated M. separata during the larval, pupation and adult periods were the same as in our previous report. [26][27][28][29] Figure 7 shows dead larvae with thin and wrinkled bodies from the larval stage; Fig. 8 shows some malformed and dead pupae from the pupation stage; and Fig.…”

New Insecticidal Agents from Halogenation/Acylation of the Furyl-Ring of Fraxinellone

“…However, up to now the influence of the C-ring (furyl ring) of compound 1 to its insecticidal activity was not clear. As part of our ongoing search for new natural-product-based insecticidal agents 16 17 18 , herein we wanted to prepare a series of new fraxinellone derivatives ( VIII , Fig. 1 ) by introducing the halogen atom or the acyl group at the C-ring of 1 as insecticidal agents.…”

Synthesis Of 2′(2′,6′)-(Di)Halogenoisoxazolopodophyllic Acids-Based Amides Derived from a Naturally Occurring Lignan Podophyllotoxin and Their Acaricidal Activity

“…[15][16][17] Meanwhile, 2′(2′,6′)-(di)halogenoisoxazolopodophyllic acids-based esters (3, Figure 1) were also prepared by modified in the C and D rings, and some compounds exhibited more promising insecticidal activity than toosendanin. 18 Meanwhile, it is particularly notorious that Tetranychus cinnabarinus (Spider mite), a crop-threatening insect pest, is extremely hard to prevent and control.…”