Model studies on the synthesis of the natural meroterpenoid cordiaquinone A

Abstract

Two main strategies for the synthesis of the natural meroterpenoid cordiaquinone A (1) - isolated of the roots of Cordia corymbosa G. Don (Boraginaceae) - were tested on model compounds. Whereas all attempts of alkylation of epsilon-caprolactone (10) were unsuccessful, the coupling of epoxycitronellol (17) with an appropriate organocuprate proceeded in the expected direction.

Novel Self-Associating Poly(ethylene oxide)-block-poly(ε-caprolactone) Block Copolymers with Functional Side Groups on the Polyester Block for Drug Delivery

“…17 More importantly, the presence of an aromatic group on the PCL block seems to be even more effective than elongating the PCL block in pushing the cmc to lower concentrations. It is noteworthy to mention that the cmc value for PEO-b-PBCL is 5 times lower than the reported cmc for PEO-b-poly(β-benzyl L-aspartate) (PEO 110 -b-PBLA 19 ). The cmc value for PEO-b-PBLA measured by an identical method is 55 × 10 -2 µM.…”

“…The characteristics of prepared PEO-b-PBCL block copolymer are summarized in Table 1. The molecular weight of prepared PEO-b-PBCL block copolymer, measured by comparing the peak intensities of four methylene protons of PEO (δ ) 3.65) and two methylene protons of PBCL (δ ) 4.05) in the 1 H NMR spectrum, was calculated to be 9700 g mol -1 (equal to a degree of R-benzyl carboxylate--caprolactone polymerization of 19). A good agreement between the measured and theoretical molecular weights was observed (Table 1).…”

“…Preparation of PEO- b -PCL Block Copolymers with Aromatic Side Groups on the PCL Block. Attachment of aromatic side groups to PEO- b -PCL block copolymer was carried out through conjugation of benzyl chloroformate with ε-caprolactone monomer producing α-benzyl carboxylate-ε-caprolactone monomer (Scheme ) , and further ring-opening polymerization of this new monomer by methoxy-PEO (Scheme ). In preliminary studies, direct conjugation of benzyl carboxylate group to PEO- b -PCL block copolymers through generation of lithium carbanion on the PCL block following treatment with lithium diisopropylamine (LDA) was tried, as suggested by Gimenez et al and Ponsart et al for homopolymers of PCL. , This approach led to a loss in the intensity of peak at δ = 3.65 ppm in the 1 H NMR spectrum of product reflecting the loss of PEO chain during the formation of polycarbanion (data not shown).…”

“…The temperature was allowed to rise to 0 °C, and the reaction was quenched with 5 mL of saturated ammonium chloride solution. 19 The reaction mixture was diluted with water and extracted with ethyl acetate. The combined extracts were dried over Na 2 SO 4 and evaporated.…”

“…ε-Caprolactone (3.42 g) was dissolved in 8 mL of dry THF and added to the above-mentioned mixture slowly, followed by the addition of benzyl chloroformate (5.1 g). The temperature was allowed to rise to 0 °C, and the reaction was quenched with 5 mL of saturated ammonium chloride solution …”