--- title: "Bioisosteres Template – Chemistry Diagram | MolDraw" url: https://www.moldraw.com/templates/medchem-bioisosteres/ description: "Bioisosteres template: Carboxylic acid ↔ tetrazole, amide ↔ 1,2,3-triazole and 1,2,4-oxadiazole, phenyl ↔ pyridine and thiophene, and H ↔ F, each with what…" lang: en publisher: Scidart Academy generated: 2026-10-28 --- [MolDraw](https://www.moldraw.com/) › [Templates](https://www.moldraw.com/templates/) › [Medicinal chemistry](https://www.moldraw.com/templates/medicinal-chemistry/) › Bioisosteres [Medicinal chemistry](https://www.moldraw.com/templates/medicinal-chemistry/)Premium # Bioisosteres template ![Bioisosteres template: Carboxylic acid ↔ tetrazole, amide ↔ 1,2,3-triazole and 1,2,4-oxadiazole, phenyl ↔ pyridine and thiophene, and H ↔ F, each with what it changes, plus losartan with its tetrazole circled.](https://www.moldraw.com/templates/medchem-bioisosteres.webp) [Edit in MolDraw](https://www.moldraw.com/)Download with Pro Premium template. Preview and edit it free in MolDraw; downloading and exporting it is part of [MolDraw Pro](https://www.moldraw.com/pricing). Carboxylic acid ↔ tetrazole, amide ↔ 1,2,3-triazole and 1,2,4-oxadiazole, phenyl ↔ pyridine and thiophene, and H ↔ F, each with what it changes, plus losartan with its tetrazole circled. ## What the template shows - Swap a group for one with similar shape and electronics to fix potency, metabolism or properties - Classical and non-classical replacements - Carboxylic acid ↔ 1H-tetrazole - carboxylic acid - 5-substituted 1H-tetrazole - Both acidic (pKa ≈ 4–5 vs 4.5–4.9) and anionic at pH 7.4; the tetrazole spreads the charge over a larger, more lipophilic ring and avoids acyl glucuronides. Losartan, valsartan. - Amide ↔ 1,2,3-triazole / 1,2,4-oxadiazole - secondary amide - 1,4-disubstituted 1,2,3-triazole - Planar, same substituent vectors and H-bond acceptors as the amide, but no hydrolysable C(=O)–N: protease and amidase stable. The triazole comes from CuAAC click chemistry. - Phenyl ↔ pyridine / thiophene - Ring N lowers log P, adds an H-bond acceptor and improves solubility; thiophene is the classical isostere of benzene (similar size and aromaticity). - F is the smallest substituent after H (van der Waals radius 1.47 vs 1.20 Å). A para-F blocks CYP450 hydroxylation at that site and changes pKa and lipophilicity (atorvastatin, ezetimibe). - In a drug: losartan - AT₁ antagonist: the tetrazole replaced a CO₂H of the lead and raised oral activity - Tetrazole (circled) in place of the biphenyl carboxylic acid: same anion at pH 7.4, better oral absorption and potency (Meanwell 2011). - Biphenyl tetrazole became the “sartan” pharmacophore: valsartan, irbesartan, candesartan. - A bioisostere keeps the biological activity while changing something else: pKa, log P, metabolic stability, toxicity or patent position. - Classical isosteres match valence and size (–CH₂– / –O– / –NH–, H / F, benzene / thiophene); non-classical ones match the job (tetrazole for CO₂H, triazole for amide). - No replacement is neutral: always re-measure potency, permeability and solubility. Context decides whether a swap works. - R = the rest of the molecule; circles mark the atoms that change. - Meanwell, J. Med. Chem. 2011, 54, 2529 · every part of this sheet is editable Drawn with 94 atoms, 24 shapes – every one editable in MolDraw. ## Sources - [Meanwell, J. Med. Chem. 2011, 54, 2529](https://doi.org/10.1021/jm1013693) Review - [Patrick, An Introduction to Medicinal Chemistry, 6th ed., OUP 2017](https://openlibrary.org/isbn/9780198749691) Textbook ## How to use this template 1. Press **Edit in MolDraw**. The template opens on the canvas of the free MolDraw editor. 2. Change anything: move structures, edit atoms and labels, recolour highlights or delete what you do not need. 3. Add your own structures, arrows and text next to it, or combine several templates on one page. 4. Export the drawing as PNG, SVG or PDF for slides, worksheets, theses and papers. ## Frequently asked questions ### Is the Bioisosteres template free? You can preview the Bioisosteres template here and open and edit it in MolDraw for free. Downloading or exporting it is part of MolDraw Pro, together with the other premium templates. ### Can I edit the Bioisosteres template? Yes. It opens as an ordinary MolDraw drawing, so every structure, arrow, label and colour can be changed, and you can add your own content around it. ### Is the chemistry checked? Every structure is checked with RDKit and every curly arrow passes MolDraw’s electron-flow audit. The sources used are listed on this page. ### Are the drug structures accurate? Every structure is checked with RDKit, including its stereocentres, and the sheets follow the medicinal chemistry textbooks listed on each template page. ## More medicinal chemistry templates [**Lipinski rule of five**Free · Medicinal chemistry](https://www.moldraw.com/templates/medchem-lipinski-rule-of-five/)[**β-Lactam antibiotics**Free · Medicinal chemistry](https://www.moldraw.com/templates/medchem-beta-lactam-antibiotics/)[**Statins: HMG-CoA reductase inhibitors**Free · Medicinal chemistry](https://www.moldraw.com/templates/medchem-statins/)[**NSAIDs and cyclooxygenase**Premium · Medicinal chemistry](https://www.moldraw.com/templates/medchem-nsaids-cox/)[**Prodrugs**Premium · Medicinal chemistry](https://www.moldraw.com/templates/medchem-prodrugs/) ## Related pages [**Functional Groups Identification Worksheet**Free printable worksheet](https://www.moldraw.com/educational-materials/functional-groups-identification-worksheet/)[**All Medicinal chemistry templates**6 templates](https://www.moldraw.com/templates/medicinal-chemistry/)[**All chemistry templates**370 templates in 29 categories](https://www.moldraw.com/templates/) MolDraw Pro Download all 370 templates - Export the 291 premium templates as PNG, SVG or PDF - AI chemistry assistant - Structure scanning from images - Cloud save and teaching slides [See Pro plans](https://www.moldraw.com/pricing) Free templates stay free. 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