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Organic Building Blocks

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Functionalised scaffolds bought in so a route can start from structure rather than build it. The decision here is rarely which compound — that follows from the target — but whether the material you can buy at ten grams for the medicinal chemistry will still be available, at a workable price and specification, at the ten kilograms the first campaign needs.

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In this range

Listed on the TSS storefront and searchable there by name or CAS number. Every enquiry is contracted and invoiced by Taitil Global Inc. in the United States or Europe.

Specifying it

What decides the purchase

The compound is usually fixed by the route. These are the things that vary between suppliers and between lots.

  1. Protecting-group state is part of the compound

    Boc-, Cbz- and Fmoc-protected versions of the same amine are different materials with different stability, different deprotection conditions and often very different prices. The catalogue name may not distinguish them clearly. Check the CAS number, and state which protected form the route expects rather than which parent structure it is based on.

  2. Chirality: enantiomeric excess, and how it was measured

    For a chiral building block, ee is the specification that matters and the method behind it is part of the claim. Chiral HPLC with the column and conditions stated is verifiable; a bare '98% ee' is not. Ask also whether the ee is of the lot or of the process — those are not the same number, and the difference shows up when a later lot sits at the bottom of the range.

  3. Ask the scale-up question before the route is fixed

    Many building blocks are made in gram quantities for screening and have no established route at kilogram scale. Establishing that a scaffold is available in the quantity a campaign will need, at a lead time the programme can absorb, is worth doing while the route can still be changed. It is a cheap question early and an expensive one late.

  4. Isomeric and positional purity, separately from assay

    As with heterocycles, the meaningful figure is often not the assay but what the balance consists of. A positional isomer carries through the sequence; a residual solvent does not. Where the scaffold has more than one reactive site, ask specifically about the isomer content rather than accepting a single purity number.

Questions

Is a building block available at kilogram scale if it is listed in grams?
Not automatically. Many are prepared to order in small quantities and have no validated route at scale, so lead time and price at kilogram level can differ by more than an order of magnitude. Ask before the route depends on it — the answer occasionally changes which scaffold a programme should be built around.
How should enantiomeric excess be reported?
As a percentage for the named enantiomer, with the analytical method and conditions stated — typically chiral HPLC with the column, mobile phase and detection given. A figure without a method behind it cannot be checked, and 'chiral purity' used loosely sometimes means diastereomeric rather than enantiomeric excess.
Do protected and unprotected forms need separate specifications?
Yes, and they usually need separate suppliers' certificates too. They are distinct compounds with distinct CAS numbers, stability profiles and storage requirements. Ordering the parent structure when the route needs the Boc-protected form is one of the commoner ordering errors in this class, and the CAS number is what prevents it.