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. Author manuscript; available in PMC: 2012 Mar 23.
Published in final edited form as: Angew Chem Int Ed Engl. 2010 Jul 26;49(32):5489–5493. doi: 10.1002/anie.201001151

Figure 1. Retrosynthetic analysis for the preparation of human KP-insulin by the ‘ester insulin’ strategy.

Figure 1

KP-insulin is a fast acting form of human insulin in which the native ProB28-LysB29 sequence is inverted to LysB28-ProB29.[23] KP-insulin coordinates are from Protein Databank entry 1LPH.[24] Insulin A-chain is shown in red, B-chain in green, and GluA4 and ThrB30 in cyan. The γ-CH3 and β-OH of ThrB30 are not visible due to disorder in the crystal structure; however, the possible positions of the β-OH of ThrB30 can be accurately inferred since the position of the ThrB30 β-carbon is known. The desired ester linked molecule (1) was prepared by native chemical ligation[25] of [PheB1-ValB18]-αthioester and the ester linked CysB19-[A1-GluA4(OβThrB30)-A21] peptide as described in the Supporting Information.