A powerful advantage of CPS is the ability to produce mirror-image D-proteins (made of D-amino acids), which cannot be obtained through other means. D-proteins have enabled techniques such as racemic crystallography for facile refinement of protein structures and mirror-image phage display for the discovery of proteolytically stable D-peptide drugs. Fewer than 30 D-protein syntheses have been reported 4 , and many of these are among the largest proteins synthesized to date, 27,32-37 each a remarkable achievement. To enable more routine access to larger D-proteins, a long-term goal in the CPS field is the synthesis of a complete mirror-image ribosome, which could produce virtually any size of D-protein via in vitro translation. The minimal E. coli ribosome (including 11 accessory factors) is an ambitious synthetic target comprised of 65 proteins ranging from 38 to 890 aa (see our previous Aligator report for more information on these proteins). To simplify this challenge, we sought to apply our bracket-building tools to lay out an initial blueprint and identify the most daunting obstacles.