Table 1. Optimization of Kdo-(2 → 4)-Kdo Glycoside Formation.

					isolated yields (%)
entry	donor [equiv]	BF3·Et2O [equiv]	T [°C]	time [min]	21	22	20
1	2	2.1	0	120	40	16	20
2	1.5	1.6	0	100	52	25	12
3	1.5	1.6	–20	120	40	42	traces
4a	1.5	1.6	0	25	22	6	50
5b	1.5	1.6	0	100	11	5	65
6c	1.5	1.6	0	100	23	12	30

^aBF₃·Et₂O was slowly added during 20 min using a syringe pump.

^bReaction was carried out with 1 equiv of NEt₃.

^cReaction was carried out with 1 equiv of DIPEA.