Practical Synthesis of 5,7-Dichlorotetrahydroisoquinoline-6-carboxylic Acid-Key Intermediate of Lifitegrast (Xiidra)

In the present study, a practical method for synthesizing the key intermediate 5,7-dichlorotetrahydroisoquinoline-6-carboxylic acid (1) of Lifitegrast was proposed. First, an investigation was conducted into the utilization of the impurity and recrystallization method in the synthesis of 5,7-dichlorotetrahydroisoquinoline (5·HCl) via Friedel-Crafts cyclization. Through the screening of different protection groups, a previously unreported quaternary ammonium salt (13) was isolated with a 95.9% yield and 99.6% purity by simply adjusting the pH during the carboxylation reaction. Subsequently, free state 1 was obtained by controlling the pH to 4-5 with HCl(aq), thereby avoiding the need for a free operation in the synthesis of the API of Lifitegrast. Further, the triphenylmethanol (TrOH) was recycled to triphenylmethyl chloride (TrCl) using CaCl₂/HCl(aq) with 93.0% yield and 98.0% purity.

Structure and Activity of the Camellia oleifera Sapogenin Derivatives on Growth and Biofilm Inhibition of Staphylococcus aureus and Escherichia coli

Sapogenin is the main block of Camellia oleifera saponin, which was purified and structurally modified by the C₂₈ acylation reaction to synthesize 19 new derivatives. The growth and biofilm inhibition of Staphylococcus aureus and Escherichia coli was measured to evaluate their antibacterial effects. A three-dimensional quantitative structure-activity relationship (3D-QSAR) assay indicated that the antibacterial activities were significantly enhanced after sapogenin was modified with an aromatic ring or heterocyclic ring and electron-withdrawing substituents at the meta or para position. Among them, the derivative of sapogenin with a 2-mercapto-4-methyl-5-thiazolyl acetyl group obviously destroyed bacterial biofilm and made bacteria lysis. 3D-QSAR provides practical information for the structural design of sapogenin derivatives with strong antibacterial activity, and the C. oleifera sapogenin derivative 28-O-(2-mercapto-4-methyl-5-thiazolyl)-3β,16α,21β,22α-O-tetrahydroxy-oleantel-2-ene-23-aldehyde (S-16) is an effective candidate as an antibacterial agent for the prevention of bacterial resistance against antibiotics.