1. Synthesis and NMR characteristics of N-acetyl-4-nitro, N-acetyl-5-nitro, N-acetyl-6-nitro and N-acetyl-7-nitrotryptophan methyl esters
Russell R King, Larry A Calhoun Magn Reson Chem. 2009 Mar;47(3):273-6. doi: 10.1002/mrc.2377.
N-acetyl-4-nitrotryptophan methyl ester (2), N-acetyl-5-nitrotryptophan methyl ester (3), N-acetyl-6-nitrotryptophan methyl ester (4) and N-acetyl-7-nitrotryptophan methyl ester (5) were synthesized through a modified malonic ester reaction of the appropriate nitrogramine analogs followed by methylation with BF(3)-methanol. Assignments of the (1)H and (13)C NMR chemical shifts were made using a combination of (1)H-(1)H COSY, (1)H-(13)C HETCOR and (1)H-(13)C selective INEPT experiments.
2. O-Methylation of carboxylic acids with streptozotocin
Li-Yan Zeng, Yang Liu, Jiakun Han, Jinhong Chen, Shuwen Liu, Baomin Xi Org Biomol Chem. 2022 Jul 6;20(26):5230-5233. doi: 10.1039/d2ob00578f.
The clinically used DNA-alkylating drug streptozotocin (STZ) was investigated using a simple work-up as an O-methylating agent to transform various carboxylic acids, sulfonic acids and phosphorous acids into corresponding methyl esters, and did so with yields of up to 97% in 4 h at room temperature. Good substrate tolerance was observed, and benefited from the mild conditions and compatibility of the reaction with water.
3. Acridinium Ester Chemiluminescence: Methyl Substitution on the Acridine Moiety
Manabu Nakazono, Shinkoh Nanbu, Takeyuki Akita, Kenji Hamase J Oleo Sci. 2021;70(11):1677-1684. doi: 10.5650/jos.ess21186.
Methyl groups were introduced on the acridine moiety in chemiluminescent acridinium esters that have electron-withdrawing groups (trifluoromethyl, cyano, nitro, ethoxycarbonyl) at the 4-position on the phenyl ester. The introduction of methyl groups at the 2-, 2,7-, and 2,3,6,7-positions on the acridine moiety shifted the optimal pH that gave relatively strong chemiluminescence intensity from neutral conditions to alkaline conditions. 4-(Ethoxycarbonyl)phenyl 2,3,6,7,10-pentamethyl-10λ4-acridine-9-carboxylate, trifluoromethanesulfonate salt showed long-lasting chemiluminescence under alkaline conditions. Acridinium esters to determine hydrogen peroxide concentration at pH 7-10 were newly developed.
