Chemical macrolactonization of precursor 22.

Entry	Reagents	Molar volume (mL mmol−1)	Yielda (%)
1	DCC, DMAP, PPTs	860	64
2	DCC, DMAP, PPTs	60	40
3	DMC, DMAP	60	67
4	DMC, DMAP	15	71
5	DMC, DMAP, Cs2CO3	60	47b
6	DMC, DMAP, KOTf	60	80b
7	DMC, DMAP, KOTf	15	73

^aIsolated yield.

^bTraces of dimer were detected.