ZINC Chemical Library Database (ZINC22 / CartBlanche)

Overview

ZINC (ZINC Is Not Commercial) is a free database of commercially available compounds curated for virtual screening. The current generation, ZINC22, holds billions of make-on-demand and in-stock molecules and is served through the CartBlanche web application at cartblanche22.docking.org. CartBlanche exposes a small JSON API to look up substances by ZINC ID, resolve a SMILES to its ZINC identifier, and inspect supplier/catalog purchasability.

Important — the old ZINC15 REST API no longer works for automated access. zinc15.docking.org (and zinc.docking.org) now sits behind a site-wide CAPTCHA: every request to /substances.json, /tranches/..., /substances/{id}.json, etc. is redirected to a /captcha/ page or returns 403 Forbidden. Any script using the mwt__gte / availability / similarity query parameters against zinc15.docking.org will fail. Use the ZINC22 CartBlanche endpoints documented below instead.

Three things about ZINC22/CartBlanche that change how you use this skill:

1. There is no server-side property-range query. ZINC22/CartBlanche has no mwt__gte / logp__lte / hbd__lte search. You filter by molecular property by either (a) selecting tranches (a 2D MW x logP grid) for bulk download, or (b) retrieving compounds and filtering locally with RDKit. This skill shows the local-RDKit approach.
2. SMILES lookup is asynchronous. You POST a SMILES, receive a task id, and poll for the result. Exact-match lookup completes in seconds.
3. Reliable programmatic search = exact match. The API's broader analog search (dist > 0) is slow and frequently times out on the public server, and the Smallworld similarity search is a website-only flow. Treat exact SMILES → ZINC ID lookup as the dependable primitive; see the "Analog / Similarity Search" note for the (limited) alternatives.

When to Use