A variation of Mattox rearrangement mechanism under alkaline condition

Optimization of the synthesis of a key intermediate for the preparation of glucocorticoids

A short and efficient synthesis, based on a one-step double elimination, of a key intermediate in the synthesis of various glucocorticosteroids has been developed. This method can be carried out on large scale for further industrial applications. The synthesis allowed us to identify a novel prednisolone derivative 10 and its anti-inflammatory activity was determined in an in vivo model of inflammation. In order to understand the regioselectivity of the double elimination under various conditions, mechanistic studies were undertaken and confirmed the experimental results. We also propose a mechanism for the formation of the new steroid 10 studied by molecular modeling.

Expedient synthesis of 17α,21-dihydroxy-9β,11β-epoxy-16α-methylpregna-1,4-diene-3,20-dione 21-acetate from prednisolone utilising a novel Mattox rearrangement

A six step transformation of prednisolone to 17α,21-dihydroxy-9β,11β-epoxy-16α-amethylpregna-1,4-diene-3,20-dione 21-acetate has been achieved in 13% unoptimised yield. Novel conditions for effecting a Mattox rearrangement and double dehydration of prednisolone were identified. Enhanced knowledge on the oxidation of silyl Δ(19,20)-enol ethers and structural factors that impact the success of the oxidation are also presented.

Use of liquid chromatography/tandem mass spectrometric molecular fingerprinting for the rapid structural identification of pharmaceutical impurities

Use of liquid chromatography/tandem mass spectrometric (LC/MS(n)) molecular fingerprinting is systematically demonstrated as a very effective tool for rapid structural elucidation of pharmaceutical impurities through a case study in which three isomers of betamethasone sodium phosphate (BSP) were rapidly identified as degradants formed due to the D-homoannular ring expansion of the steroid core structure of BSP in the solid state. The rapid structural elucidation of these degradants was achieved by matching or closely matching the UV profiles, molecular weights, and more importantly the fragmentation patterns obtained from the LC/MS(n) (n = 1 to 3) analysis of their enzyme-catalyzed hydrolytic products, respectively, with those of a D-homoannular isomer of betamethasone available in our LC/MS(n) molecular fingerprint database. This strategy of using LC/MS(n) molecular fingerprinting to obtain high-confidence structures of unknown species is then validated by structure verification through one- (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) experiments.

A comparative study of enol aldehyde formation from betamethasone, dexamethasone, beclomethasone and related compounds under acidic and alkaline conditions

Enol aldehydes are one type of key degradation and metabolic intermediates from a group of corticosteroids containing the 1,3-dihydroxyacetone side chain on their D-rings, such as betamethasone, dexamethasone, beclomethasone, and related compounds. The formation of enol aldehydes from these corticosteroids is via acid-catalyzed beta-elimination of water from the side chain, a process known as Mattox rearrangement. It was recently reported by our group that enol aldehydes could also be formed directly from the corresponding 17,21-diesters of these corticosteroids but only under alkaline condition, which was proposed to follow a variation pathway of the original Mattox rearrangement. In this paper, we report the results of a comparative study of enol aldehyde formation from these structurally similar corticosteroids (under the original acidic Mattox condition) and their 17,21-diesters (under the alkaline Mattox variation condition), respectively. In general, enol aldehydes were found to be formed under both conditions; however, the ratios of the E- and Z-isomers of the enol aldehyde were different in each case. The only exception was beclomethasone 17,21-diester under the alkaline condition, where a competing elimination of HCl from the 9,11-positions became predominant. These results can be explained by their structural differences with regard to the Mattox mechanism and its variation pathway. Lastly, solvent effect under acidic condition was studied between an aprotic and a protic solvent and the result suggests that enol aldehyde formation is greatly favored in an aprotic environment.