Concise synthetic routes to human insulin.

We report a set of concise and efficient routes for the chemical synthesis of human insulin using a two- or three-step combination procedure that employs Trt, Acm, and t-Bu cysteine protection schemes. Starting with resin-bound assembled A and B chains, human insulin can be obtained within the span of a single work day in 5.4% overall yield based on the crude A or B chain.