Beads displaying these molecules were then subjected to the reaction conditions described above using 2-formyl-quinoline to close the macrocycle. After release from the beads the products were analyzed by LC-MS (see Supplementary Figures ). Compound MP2, in which no spacer alanine was present, was produced in only about 5% LC yield. A single alanine spacer resulted in about half of the starting material being converted to the desired product. The linear peptides containing 2-5 alanine units provided a high yield of clean product. The yield decreased again using peptides containing 6-9 alanine residues.