Table 1.

Synthesis of betulin derivatives 2–7.

Entry	Substrate				Product
	No.	Solvent	Temp., °C	Time, h	No.	R (C3)	R1 (C28)	Yield, %
1	1	THF	r.t.	24	2	OH	OCH2C≡CH	54
					3	OCH2C≡CH	OCH2C≡CH	31
2	1	THF	r.t.	24	4	OH	O(CO)CH2Cl	34
3	1	THF	r.t.	24	5	O(CO)CH2Cl	O(CO)CH2Cl	95
4	4	DMF	90	3	6	OH	O(CO)CH2N3	64
5	5	DMF	90	3	7	O(CO)CH2N3	O(CO)CH2N3	72