The SgcC5 condensation enzyme catalyzes the attachment of SgcC2-tethered (S)-3-chloro-5-hydroxy-β-tyrosine (2) to the enediyne core in C-1027 (1) biosynthesis. It is reported that SgcC5 (i) exhibits high stereospecificity toward the (S)-enantiomers of SgcC2-tethered β-tyrosine and analogues as donors, (ii) prefers the (R)-enantiomers of 1-phenyl-1,2-ethanediol (3) and analogues, mimicking the enediyne core, as acceptors, and (iii) can recognize a variety of donor and acceptor substrates to catalyze their regio- and stereospecific ester bond formations.