I am planning to design and synthesis of novel small inhibitors/antagonist of TLRs.
How should I begin? I have requested many private companies to provide samples but they could'nt provide as per their policies. So please help in this regard.
What do you mean? Of course they don't have samples if it's "custom" (as in, not already sitting on the shelf). You need to hire someone to figure out how to make it. If it's really a new molecule, then nobody can give you guarantees. If you want to evaluate someone's ability to do a custom project, try things like asking them what kinds of similar projects they have done before, and see if what they're talking makes sense.
I would start searching for similar compounds and check or their is a known route on Scifinder or reaxys. Try to change structures to more easy structures if you are unable to find anything. I geuss this when synthesizing new compounds using novel routes will always be an insecurity and even this approach might not enable you to synthesize the molecule.
What I know from custom synthesis companies is that they have far more knowledge in their database then what you can find online. For your question it is probably to late but if you are ever considering custom synthesis you can always ask for a quote. I work part time for 007chemicals, if you have a request they will always be happy to answer. We are only specialised in small molecules and mainly produce heterocycles so keep in mind that dependent of your needs other companies might be more applicable (think about protein or peptide synthesis).