We also explored the thermal cyclodehydration of Fmoc-protected dipeptides 23 -27. With the exception of oxidationprone methionine 25, the oxazolines were successfully synthesized. These results, along with the synthesis of thiazolines 9 -10, highlight a potential application of the Mo(VI)-catalyzed cyclodehydration in Fmoc protected solid phase peptide synthesis of azole/azoline containing peptides. To further probe the scope of the new catalytic system, cyclizations of aromatic derivatives were successfully accomplished (2, 28, 95%, 95%). This includes reactions with heteroaryl-2oxazolines such as bis-oxazoline 29, synthesized from isoleucine in 55% yield and thiophene 30, prepared in 63% yield. In reactions where the formation of two azoline products could directly compete, thiazoline formation was slightly favored over oxazoline formation and two isomers 32a:32b were obtained as a 1.00:2.51 ratio of inseparable products. Additionally, mandelic acid derivative 33, with an α-hydroxycarbonyl was found to undergo oxidation to α-ketoamide 34 under the typical cyclization conditions without producing any of oxazoline 35 or the corresponding α-hydroxy oxazoline product. We then attempted cyclization on the α-ketoamide 34, obtaining oxazoline 35 in acceptable yield (53%).