08 m 4h 0 98 0 71 m 6h product 24 142 0 mg 63 9 for two steps lc ms m z 770 0 m h 1 h nmr 400 mhz dmso u03b4 presumable a mixture of rotamers 8 98 d j 8 0 hz 8 67 d j 8 0 hz 8 52 8 31 m 2h 7 85 dd j 16 0 hz 4 0 hz 1h 7 65 dd j 16 0 4 0 hz 1h 7 37 7 10 m 5h 5 50 5 25 m 2h 4 80 4 20 m 3h 3 65 3 35 m 3h 3 35 3 15 m 7h 3 10 2 60 m 6h 2 40 1 89 m 5h 1 90 1 50 m 8h 1 55 1 35 m 8h 1 35 1 15 m 8h 1 08 0 71 m 6h conjugation of a drug molecule with vc val cit pabc mc maleimidocaproyl or peg linker followed known procedures in wo2004010957 and us 20050238649a1 the yields of linkage of varieties of drugs with cleavable linker vc and non cleavable linker mc were shown in table 1 to a solution of mcvalcitpabc 1 0 eq and drug 23 1 0 eq in dmf was added hunig 39 s base 4 eq 2 6 lutidine 4 eq and hoat 0 2 eq the reaction mixture is allowed to stir for 30 minutes at room temperature reaction is monitored by lc ms after the completion the reaction is concentrated and purified by flash chromatography then by c 18 medium pressure reversed phase chromatography gradient 5 acetonitrile to 100 acetonitrile containing 0 1 tfa 27 20 0 mg 36 1 lc ms m z.