A final 14 residue model peptide (50) was prepared to explore the preparation of larger (44mer) macrocycles. Under the optimised cyclisation conditions the starting peptide was fully consumed to afford an inseparable mixture of the desired cyclised product and the desulfurised linear by-product. Increasing the mol% of the PC to 5% resulted in the formation the postulated phosphonium by-product observed for acrylamide model 13 (Figure ). This by-product (51) was isolated in 58% yield; P NMR analysis gave a single phosphorus resonance at 36.6 ppm. Thus, while the reported strategy is highly effective for the formation of peptide macrocycles up to 26mer (tolerating the full range of proteinogenic chemical functionality), larger macrocycles are inaccessible using this approach.