N n diisopropylcarbodiimide dic

Ferulic acid (99%) and triphenyl phosphine (99%) were purchased from Sigma-Aldrich Japan Co., Ltd. p-Coumaric acid (>98.0%), sinapinic acid (>98.0%), oxalyl chloride (>98.0%), and diisopropyl azodicarboxylate (40% in toluene, ca. 1.9 mol L⁻¹) were purchased from Tokyo Chemical Industry Co., Ltd. Methyl ricinoleate (>97.0%), acetic anhydride (>97.0%), N,N-dimethylaminopyridine (DMAP) (>99.0%), N,N′-diisopropylcarbodiimide (DIC) (>99.0%), pyridine (>99.5%, dehydrated), N,N-dimethylformamide (DMF) (>99.5%, dehydrated), sodium sulphate (Na₂SO₄) (>99.0%), and tetrahydrofuran (THF) (>99.5%, with stabilizer, for gel permeation chromatography (GPC) grade) were purchased from FUJIFILM Wako Pure Chemical Corporation. p-Toluenesulfonic acid monohydrate (>99.0%) and lithium hydroxide monohydrate (>99.0%) were purchased from KISHIDA CHEMICAL Co., Ltd. Toluene (>99.5%, dehydrated), dichloromethane (CH₂Cl₂) (>99.5%, dehydrated), and THF (>99.5%, dehydrated stabilizer free) were purchased from Kanto Chemical and purified on a Glass Contour Solvent Purification System (NIKKO HANSEN & Co., Ltd, Japan). Chloroform-d₁ (99.8 atom % D with 0.03 vol% tetramethylsilane) was purchased from Kanto Chemical. These chemicals were used without further purification unless otherwise noted. 4-(Dimethylamino)pyridinium p-toluenesulfonate (DPTS) was synthesised according to the literature.^{43 (link)}