The antitumor tetrahydroisoquinoline (THIQ) alkaloids share a common pentacyclic scaffold that is biosynthesized by nonribosomal peptide synthetases involving unique enzymatic Pictet Spengler cyclizations. Herein we report concise and divergent chemoenzymatic total syntheses of THIQ alkaloids by merging precise chemical synthesis with in vitro engineered biosynthesis. A recombinant enzyme SfmC responsible for the biosynthesis of saframycin A was adapted for the assembly of these natural products and their derivatives, by optimizing designer substrates compatible with SfmC through chemical synthesis. The appropriately functionalized pentacyclic skeleton were efficiently synthesized by streamlining the linkage between SfmC-catalyzed multi-step enzymatic conversions and chemical manipulations of the intermediates to install aminonitrile and N-methyl groups. This approach allowed rapid access to the elaborated pentacyclic skeleton in a single day starting from two simple synthetic substrates without isolation of the intermediates. Further functional group manipulations allowed operationally simple and expeditious syntheses of jorunnamycin A, saframycin A, and N-Fmoc saframycin Y3 that could be versatile and common precursors for the artificial production of other antitumor THIQ alkaloids and their variants.