Below are widely used B2B portals and marketplaces for pharmaceutical sourcing, grouped by use-case (APIs/raw materials, R&D/compounds, broad B2B portals). I included one trusted source for each entry so you can check specifics.

Specialized pharma portals / supplier directories

• PharmaCompass — searchable marketplace and supplier directory for APIs, FDFs, intermediates, excipients; includes verified-supplier services and market intelligence. (pharmacompass.com)
• PharmaSources — global marketplace listing finished dosage forms, APIs, intermediates and equipment (supplier catalog-style). (pharmasources.com)
• PharmaHopers — directory / B2B marketplace focused on pharma manufacturers, exporters and distributors. (pharmahopers.com)

Life‑science & R&D marketplaces (good for discovery compounds, building blocks, reagents)

• eMolecules — large chemical/compound search-and-procurement platform used by pharma R&D (tens of millions of part numbers / structures). Good for screening compounds, building blocks and custom synthesis. (emolecules.com)
• ZAGENO — life‑science marketplace for lab reagents, consumables and equipment (broad supplier network; widely used by research and biotech teams). (zageno.freshdesk.com, accessnewswire.com)
• MolPort — R&D compound sourcing portal (stock screening compounds, building blocks; vetting/fulfilment services). (molport.com, technologynetworks.com)

Chemical / supplier index platforms (useful for intermediates, excipients, hard‑to‑find reagents)

• ChemBlink — large searchable chemical/supplier index (CAS‑driven listings and supplier links). (chemblink.com)
• Volza / Accio / EC21 — trade-data driven supplier/search platforms and B2B portals that aggregate chemical and pharma-grade listings. (Useful to identify exporters/importers and shipment history.) (volza.com, accio.com, ec21.com)

Large general B2B marketplaces (broad reach but exercise extra QA)

• Alibaba / Global Sources / IndiaMART / TradeIndia — very large international B2B marketplaces where many API/excipient/ingredient suppliers are listed. These can be useful for sourcing contacts and price discovery, but require strict supplier verification because marketplaces are heterogeneous in quality and some pharma listings have been restricted or flagged in the past. (alibaba.com, en.wikipedia.org, storehippo.com)

Short vendor‑qualification and compliance checklist (recommended)

• Require supplier GMP / ISO certificates and current Certificates of Analysis (CoAs) for each batch; confirm the manufacturing site listed on the CoA. (FDA Q7A and industry GMP expectations for APIs.) (fda.gov)
• Prefer WHO‑prequalified products or suppliers with recognized regulatory approvals (where applicable); use WHO prequalification / procurement guidance for bulk purchasing. (who.int)
• Do an audit or third‑party analytical testing (identity, purity, residual solvents) on samples before large orders. Maintain full traceability (batches, bills of lading, original manufacturer). (fda.gov)
• Check sanctions/blocked‑party lists, customer references, on‑site audit reports and buyer‑side performance history (lead times, OTD). MolPort/eMolecules and similar marketplaces publish supplier performance/tiering information. (webdev.molport.com, emolecules.com)

Quick notes / risks

• Large general marketplaces are useful for lead generation and price discovery but carry higher counterparty risk — verify regulatory compliance and test materials. Alibaba in particular has limited or changed policies on listing of pharma products in recent years, so confirm current platform rules and supplier credentials. (cphi-online.com, alibaba.com)

If you want, I can:

• produce a short list of vetted suppliers for a specific API, excipient or region; or
• produce a downloadable checklist/template RFQ and supplier‑due‑diligence form you can use when contacting sellers.

(If you’d like any of those, tell me the product class or region and I’ll prepare it.)