Which organic compounds cannot be synthesised in a laboratory?

Generally, you can synthesize all of the enzymes responsible for the biosynthesis of a molecule, immobilize them and create a reactor that will synthesize the desired product. Vitamins, for example, are organic compounds that are necessary for body metabolism. Vitamins usually cannot be synthesized in amounts sufficient enough, and therefore must be obtained from the diet or some synthetic source.

Synthesis begins from the basic laboratory compounds and yields something new, and it is purely a chemical process. If synthesis starts from a product isolated from plants and animals, and then it proceeds to new compounds. The combination is a semi-synthetic process.