Monascorubramin synthesis

Yield:3627-51-8 91 mg

Reaction Conditions:

with ammonium sulfate in ethanol at 30; for 72 h;

Steps:

2.3. Chemical modification of monascorubrin

OMPs include two chemical entities: rubropunctatin (1) and monascorubrin(2), which have similar structural character and physicochemicalproperty [18,27]. According to Fig. 1B, monascorubrin (2) waschosen as target reactant for study. Monascorubrin (2) (0.1 g,0.26 mmol) in ethanol (35 mL) and primary amine ((NH4)2SO4 ormonosodium glutamate; 0.52 mmol) in water (pH 7, 15 mL) were mixed,which was stirred at 30 C for 72 h until monascorubrin was consumedcompletely (monitored by thin-layer chromatography (TLC), developingsolvent: chloroform/methanol/water 56/10/0.9). The reactionmixture was concentrated by a rotary evaporator.After evaporation of solvent, the solid residue including (NH4)2SO4was redissolved by ethyl acetate/water (1/1, V/V; 50 mL). The mixturewas transferred into a 150 mL separating funnel and an ethyl acetate layer containing monascorubramine (5) was then separated. The ethylacetate layer was concentrated in a rotary evaporator under vacuum toafford the crude product. Recrystallization of the crude pigment fromethanol yielded red needles 5 (91 mg). The purified monascorubramine(5) was further identified by MS and NMR analysis.Monascorubramine (5): Red needle solid; UV-vis (acetonitrile) max300, 415, 531 nm; HRMS Anal. Calcd for C23H26NO4, 380.1862 [M-H]-;found, 380.1853 (ESI S5). The corresponding data of 1HNMR and13CNMR analysis were presented in Table 1 and Table 2, respectively.The results are consistent with the data in literatures [26,27].

References:

Liu, Lujie;Wu, Shu;Wang, Wei;Zhang, Xuehong;Wang, Zhilong [Dyes and Pigments,2020,vol. 173,art. no. 107965]