Activation of leinamycin by thiols: a theoretical study

Area of Science:

• Medicinal Chemistry
• Computational Chemistry
• Organic Chemistry

Background:

• Leinamycin is an antitumor antibiotic featuring a 1,2-dithiolan-3-one 1-oxide heterocycle.
• Thiol reactions with this heterocycle generate a DNA-alkylating episulfonium ion, essential for leinamycin's activity.
• The electrophilic nature of the heterocycle suggests potential alternative reaction sites for thiols.

Purpose of the Study:

• To investigate the precise mechanism of thiol-mediated leinamycin activation.
• To computationally examine nucleophilic attack by thiols at all potential electrophilic centers of the leinamycin heterocycle.
• To determine the most likely pathway for leinamycin's conversion to its active form.

Main Methods:

• Computational chemistry methods were employed to study the reaction mechanism.
• Methyl thiolate was used as a model nucleophile to probe reactions with a leinamycin heterocycle analogue.
• High-level theoretical calculations (MP2/6-311+G(3df,p)//B3LYP/6-31G) were performed, including solvent effects.

Main Results:

• The study identified three potential electrophilic sites within the 1,2-dithiolan-3-one 1-oxide heterocycle.
• Computational results indicate that nucleophilic attack by thiolate preferentially occurs at the S2'-sulfenyl sulfur.
• This initial attack leads to the formation of a 1,2-oxathiolan-5-one intermediate, preceding episulfonium ion generation.

Conclusions:

• The primary mechanism for leinamycin activation by thiols involves initial thiolate attack at the S2'-position of the heterocycle.
• This pathway is more favorable than attack at the carbonyl carbon or sulfinyl sulfur.
• Understanding this mechanism is vital for the development and application of leinamycin as an anticancer agent.