semisintètiques

Semisintètiques, or semi-synthetic compounds, are substances derived from natural products through partial chemical synthesis. They retain a core structural framework of a molecule produced by nature but receive deliberate chemical modifications, such as new side chains or functional groups. This approach aims to combine the beneficial biological activity of natural products with improved properties, including broader or more targeted activity, better stability, enhanced pharmacokinetics, or easier production. The term is used in pharmacology and chemistry and appears in several languages, including Catalan, where semisintètiques is the plural form.

In medicine, semisynthetic derivatives are most prominently seen among antibiotics. Classic examples include penicillin derivatives such as ampicillin and amoxicillin, which are produced by modifying the penicillin nucleus to achieve a wider spectrum of activity or better oral absorption. Cephalosporins derived from natural cephalosporin C likewise illustrate this approach. Beyond antibiotics, semisynthetic strategies are used for steroids, anti-inflammatory agents, and other drug classes, where natural scaffolds are altered to optimize therapeutic profiles or reduce side effects.

Production typically involves isolating the natural product from a biological source and performing chemical or combined chemical-enzymatic steps to introduce new substituents or modify existing ones. This can improve receptor binding, metabolic stability, or solubility. Semisynthetic products occupy a middle ground between natural products and fully synthetic molecules, offering a balance between biological heritage and engineered properties.

See also: natural products, total synthesis, medicinal chemistry, antibiotic development.