unfortunately end product tac1 u2014 005 was not pure enough after preparative lcms resynthesis was set in and after purification by flash chromatography product tac1 u2014 005 is pure according to lcms analysis resynthesis of tac1 u2014 005 yielded eventually 25 mg of compound for the synthesis of the next class of compounds according to synthetic scheme 2 building block 1 was synthesized in low yield 1 27 g 36 this amount was enough to synthesize enough of the desired end compounds also building block 2 was prepared in high yield 456 mg 100 the first test reaction starting from building block 1 to end product tac1 u2014 011 was successful after purification by flash chromatography about 50 mg product was isolated refluxing building block 2 and isopropylamine in dichloromethane for 2 days gave complete conversion to end product tac1 u2014 012 this batch was purified by flash chromatography and yielded about 50 mg end product two reactions were performed to access the end product tac1 1009 starting from building block 1 using aqueous ammonia and 7n ammonia in meoh according to lcms tlc analysis the major compound was building block 1 73 also an unknown product 19 was present the synthesis of carbamate tac1 u2014 009 using phosgene and ammonia failed due to an unknown reason there was no change in conversion if toluene or ch 2 cl 2 was used as solvent an alternative synthesis as described below was tried resynthesis of alcohol 1 gave 1 35 g 12 after purification by silica gel column some of the alcohol was set in for the coupling with 4 nitro phenyl chloroformate to compound 3 the nitro phenol group is a far better leaving compared to.