Glucuronide synthesis using

Stevenson, D.E. and Hubl, U. (1999) Optimization of /3-D-glucuronide synthesis using UDP-glucuronyl transferase Enzyme and Microbial Technology 24, 388-396. 

There are two main types of internal standards. The first ones are stable isotope labeled (SIL) internal standards. They are compounds in which several atoms in the analytes are replaced by their respective stable isotopes, such as deuterium (2H, D or d), 13C, 15N, or 170. Labeling with the first three isotopes are most common, particularly labeling with deuterium (due to less difficulty in synthesis and therefore less expensive). For examples, raloxifene-d4-6-glucuronide was used as the internal standard for the determination of raloxifene-6-glucuronide [5] and 1, 2, 3, 4-13C4 estrone (PCJEl) was used as the internal standard for estrone (El) [6], The usage of stable isotope labeled internal standards in quantitative LC-MS or GC-MS analysis is often termed as isotope dilution mass spectrometry (IDMS) [7],... 

Microbial oxidation of drug substrates occurs in a similar fashion to mammalian oxidative biotransformation. In contrast, microbial cultures rarely catalyze conjugations comparable to those in mammalian system (glucuronidation, sulfation and GSH conjugation). It is thus not surprising that microbial bioreactors are mainly used in the synthesis of oxidative metabolites. 

Metabolite biosynthesis has demonstrated its utility in drug metabolite preparation and characterization, and contributed to drag discovery and development. Although metabolite biosynthesis is a prerequisite step for metabolite structure elucidation in many cases, it is complementary to chemical synthesis in large-scale metabolite preparations. The merits for using these techniques should be determined on a case-by-case fashion. New techniques, such as recombinant enzyme and microbial glucuronidation systems, would have a great impact on the field. 

Per-O-acylated glycosyl iodides are stable at room temperature and can be purified on a silica gel column and stored at 0 °C. Stachulski and coworkers [202] synthesized methyl 2,3,4-tri-O-pivaloyl-glucopyranuroate iodide, which is a stable solid at 20 °C and can be stored for months at room temperature or for more than a year at 0 °C. The X-ray crystal structure of this compound, the first one of this class, shows a typical chair structure. Importantly, such a disarmed and stable iodide can be coupled with primary and secondary steroidal alcohols using I2 as a promoter, as demonstrated by the synthesis of morphine-6-glucuronide, an analgesic [202], The glycosyl donor ability... 

In fact, other studies have shown that TMSOTf catalyzes the glycosylation of a silylated acceptor with a silylated hemiacetal donor [49]. Nudel man s procedure was applied to the synthesis [1-glucuronide 30, isolated in 57% yield. Kiyoi and Kondo have applied the TMSOTf activation protocol to protected L-fucose hemiacetal donors for glycopeptide synthesis and obtained glycopeptide fragment 31 in 74% yield (a p, 20 1) [50], Posner and Bull have developed a procedure that uses excess TMSOTf in the presence of molecular sieves (SYLOSIV A4) to synthesize various l.l -linked disaccharides such as the galactopyranose dimer 32 [51,52]. 

Figure 7.2 Synthesis of HOTYR glucuronides using liver cell microsomal fractions...

Koenigs-Knorr synthesis of aryl glucuronides. Steroid glucuronides of estrone, 17 /)-estradiol, estriol, and equilenin can be prepared in excellent yield by the reaction of the phenolic steroid with the bromo sugar (I) in toluene using cadmium carbonate as... 

Mycophenolate mofetil is the 2-moiphohnoethyl ester of mycophenolic acid (MPA). It is a prodrug that is rapidly hydrolyzed to the active form, mycophenolic acid. Mycophenolic acid is a selective, uncompetitive and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH). IMPDH is an important enzyme in the de novo pathway of purine nucleotide synthesis. This pathway is very important in B and T lymphocytes for proliferation. Other cells can use salvage pathways. Therefore MPA inhibits lymphocyte proliferation and functions. The mofetil ester is first converted to MPA which then is metabolized to an inactive glucuronide (Alhson and Eugui, 2000). MPA has a half-hfe of about 16 hours (Fulton and Markham, 1996). 

SCHEME 4.14 Synthesis of morphine-6-glucuronide using glycosyl iodide. 

Conrow, R B, Bernstein, S, Steroid Conjugates. VI. An improved Koenigs-Knorr synthesis of aryl glucuronides using cadmium carbonate, a new and effective catalyst, J. Org. Chem., 36, 863-870, 1971. 

The conversion of frans-retinyl acetate into retinoic acid in hamster organ culture,262 and of cis- and trans-rzimoxc acid into the 5,6-epoxy- and 4-oxo-derivatives and their glucuronides has been demonstrated.263 264 Strains of Aspergillus niger metabolize ionones and related compounds to oxygenated derivatives, some of which may be useful intermediates for carotenoid synthesis. The asymmetric oxidation of p-ionone to (25, 6/ ,7/ )-2,7-epoxydihydro-a-ionone (218) has been demonstrated.265 (i )-4-Hydroxy-p-ionone (219 X = OH)... 

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