Methods for preparing L-6-hydroxytryptophan (HTP) derivative and intermediates thereof

A method for preparing an intermediate E of L-6-hydroxytryptophan (HTP), comprising the following steps:

• subjecting a compound A6-0 to triisopropylsilyl (TIPS) protection to obtain an intermediate A of L-6-HTP;
• subjecting the intermediate A of L-6-HTP to coupling to obtain an intermediate B of L-6-HTP, wherein the coupling is conducted in the presence of (1,5-cyclooctadiene)(methoxy)iridium(I) dimer, and 1,10-phenanthroline;
• subjecting the intermediate B of L-6-HTP to carbon-boron bond oxidation to obtain the intermediate C of L-6-HTP, wherein the carbon-boron bond oxidation is conducted in the presence of sodium perborate tetrahydrate and potassium tert-butoxide (KTB), the carbon-boron bond oxidation comprises a first-stage reaction and a second-stage reaction in sequence, the first-stage reaction is conducted at a temperature of −10° C. to 10° C. for 1 h to 2 h;
• and the second-stage reaction is conducted at a temperature of 25° C. to 50° C. for 1 h to 24 h;
• subjecting the intermediate C of L-6-HTP to hydroxyl-targeted benzyl protection to obtain the intermediate D of L-6-HTP;
• and
• subjecting the intermediate D of L-6-HTP derivative to TIPS protective group removal to obtain the intermediate E of L-6-HTP;
• wherein the compound A6-0, the intermediate A of L-6-HTP, the intermediate B of L-6-HTP, the intermediate C of L-6-HTP, the intermediate D of L-6-HTP, and the intermediate E of L-6-HTP have structures shown in Formula 1, Formula 2, Formula 3, Formula 4, Formula 5, and Formula 6 respectively: