In contrast, ketone 4 is not easily sourced (no prices listed on e-molecules) and is likely the production bottleneck. This intermediate can be prepared via alkylation of aminoalcohol 5 (0.11 $/g SA, 0.04 $/g from Arcos Organics) with haloketones 6/7, which in turn can be derived from hydroxyketone 8, chloroalkyne 9, enol ethers 10a/10b, lactone 11 or chloroalkene 12. These substrates, except from 8 and 11 (both available for less than 0.5 $/g from suppliers like Combi-Blocks or ChemScene) are relatively expensive (from 4 $/g to even 585 $/g) so these methodologies are probably unsuitable for industrial up-scaling.