A compound of general formula I or pharmaceutically acceptable salts thereof: wherein, at least one of R 1 and R 2 is independently selected from: carbamoyloxy unsubstituted or substituted by one or two R 3; the other one of R 1 and R 2 is independently selected from: carbamoyloxy unsubstituted or substituted by one or two R 3, C 1-6 alkoxy unsubstituted or substituted by one to six halogen, -N(R 4) 2 or -OR 5, C 1-6 alkylacyloxy or C 7-10 arylacyloxy unsubstituted or substituted by one to six halogen, -N(R 4) 2 or -OR 5, sulfonyloxy substituted by C 1-3 alkyl or C 6-8 aryl, -OSi(R 6) 3, and -OH; W is C 1-6 alkylene or C 2-6 alkenylene unsubstituted or substituted by one to three halogen, nitro, C 1-6 alkyl, -N(R 4) 2 or -OR 5; each R is independently selected from halogen, nitro, -OR 7, -N(R 4) 2, and C 1-6 alkyl, C 6-10 aryl or C 5-9 heteroaryl, unsubstituted or substituted by one to six halogen, nitro, -N(R 4) 2 or -OR 5; n is an integer from 0 to 5; wherein, each R 3 is independently selected from: C 1-6 saturated alkyl, C 2-4 alkenyl, C 2-4 alkynyl, C 6-10 aryl, C 5-9 heteroaryl, C 1-6 alkylacyl or C 7-10 arylacyl, unsubstituted or substituted by one to six halogen, nitro, -N(R 4) 2 or -OR 5; sulfonyl substituted by C 1-3 alkyl or C 6-8 aryl; or two R 3 together with the nitrogen atom to which they are attached form a 5- to 7-membered nitrogen-containing saturated heterocyclyl (for example, 1-pyrrolidinyl, 1-piperidyl, 4-morpholinyl or 1-piperazinyl) unsubstituted or substituted by one or two R 6; each R 4 is independently -H or C 1-6 saturated alkyl; each R 5 is independently selected from -H, C 1-6 saturated alkyl, C 2-4 alkenyl, C 6-10 aryl, and C 5-9 heteroaryl; each R 6 is independently selected from C 1-6 alkyl, C 1-6 alkoxy and C 6-8 aryl, unsubstituted or substituted by one to six halogen; each R 7 is independently selected from H; C 1-6 saturated alkyl, C 2-4 alkenyl, C 2-4 alkynyl, C 6-10 aryl, C 5-9 heteroaryl, C 1-6 alkylacyl or C 7-10 arylacyl, unsubstituted or substituted by one to six halogen, N(R 4) 2 or OR 5; sulfonyl substituted by C 1-3 alkyl or C 6-8 aryl; and Si(R 6) 3. at least one of R 1 and R 2 is independently selected from: carbamoyloxy unsubstituted or substituted by one or two R 3; the other one of R 1 and R 2 is independently selected from: carbamoyloxy unsubstituted or substituted by one or two R 3, C 1-6 alkoxy unsubstituted or substituted by one to six halogen, -N(R 4) 2 or -OR 5, C 1-6 alkylacyloxy or C 7-10 arylacyloxy unsubstituted or substituted by one to six halogen, -N(R 4) 2 or -OR 5, sulfonyloxy substituted by C 1-3 alkyl or C 6-8 aryl, -OSi(R 6) 3, and -OH; W is C 1-6 alkylene or C 2-6 alkenylene unsubstituted or substituted by one to three halogen, nitro, C 1-6 alkyl, -N(R 4) 2 or -OR 5; each R is independently selected from halogen, nitro, -OR 7, -N(R 4) 2, and C 1-6 alkyl, C 6-10 aryl or C 5-9 heteroaryl, unsubstituted or substituted by one to six halogen, nitro, -N(R 4) 2 or -OR 5; n is an integer from 0 to 5; wherein, each R 3 is independently selected from: C 1-6 saturated alkyl, C 2-4 alkenyl, C 2-4 alkynyl, C 6-10 aryl, C 5-9 heteroaryl, C 1-6 alkylacyl or C 7-10 arylacyl, unsubstituted or substituted by one to six halogen, nitro, -N(R 4) 2 or -OR 5; sulfonyl substituted by C 1-3 alkyl or C 6-8 aryl; or two R 3 together with the nitrogen atom to which they are attached form a 5- to 7-membered nitrogen-containing saturated heterocyclyl (for example, 1-pyrrolidinyl, 1-piperidyl, 4-morpholinyl or 1-piperazinyl) unsubstituted or substituted by one or two R 6; each R 4 is independently -H or C 1-6 saturated alkyl; each R 5 is independently selected from -H, C 1-6 saturated alkyl, C 2-4 alkenyl, C 6-10 aryl, and C 5-9 heteroaryl; each R 6 is independently selected from C 1-6 alkyl, C 1-6 alkoxy and C 6-8 aryl, unsubstituted or substituted by one to six halogen; each R 7 is independently selected from H; C 1-6 saturated alkyl, C 2-4 alkenyl, C 2-4 alkynyl, C 6-10 aryl, C 5-9 heteroaryl, C 1-6 alkylacyl or C 7-10 arylacyl, unsubstituted or substituted by one to six halogen, N(R 4) 2 or OR 5; sulfonyl substituted by C 1-3 alkyl or C 6-8 aryl; and Si(R 6) 3.