The following three transformations also showcase the power of site-selective direct amide functionalization: (A) A one-pot mutation of carbonyl group into thioamide 33 was achieved by exposing oxazoline to H2S and produced 33 in 85% yield; (B) Regioselective reduction of 29 into amine 34 was accomplished with a borohydride; and (C) the azoline intermediate was oxidized directly into oxazole 35 albeit in a low yield, which represents a direct conversion of serine into a fully aromatic ring. We next applied the same protocol to site-selectively convert two cyclic peptides -dianthin G (36) and pseudostellarin G (37) into thioamides in the presence of seven or five other amide groups that remained intact during the entire process (Figure ). This protocol adds to the palette of methods for carbonyl thionation but also offers high regioselectivity not available with other thiophosphorus reagets. The molybdenum catalyst 2h enabled the synthesis of a series of azoline-containing cyclic peptides through direct cyclodehydration of the parent macropeptide with concomitant removal of two (38) or even three (39, 40) molecules of water. The cyclization reactions are not restricted to oxazolines, and two thiazoline groups could be readily installed, as shown in the synthesis of 40.