either or 4,4-dimethyloxetan-2-one, both of which hydrolyze under basic conditions to yield the conjugate base of HMB. The haloform reaction provides another pathway to HMB involving the exhaustive halogenation of the methyl-ketone region of diacetone alcohol with sodium hypobromite or sodium hypochlorite; Diacetone alcohol is readily available from the aldol condensation of acetone. An organometallic approach to HMB involves the carboxylation of tert-butyl alcohol with carbon monoxide and Fenton's reagent (hydrogen peroxide and ferrous iron). Alternatively, HMB can be prepared through microbial oxidation of acid by the fungus Galactomyces reessii. Detection in body fluids The concentration of naturally produced HMB has been measured in several human body fluids using nuclear magnetic resonance spectroscopy, liquid chromatography–mass spectrometry, and gas chromatography–mass spectrometry methods. In the blood plasma and cerebrospinal fluid (CSF) of healthy adults, the average molar concentration of HMB has been measured at 4.0 micromolar (μM). The average concentration of HMB in the intramuscular fluid of healthy men of ages has been measured at 7.0 μM. In the urine of healthy individuals of any age, the excreted urinary concentration of HMB has been measured in a range of micromoles per millimole (μmol/mmol) of creatinine. In the breast milk of healthy lactating women, HMB and have been measured in ranges of μg/L and mg/L. In comparison, HMB has been detected and measured in the milk of healthy cows at a concentration of μg/L. This concentration is far too low to be an adequate dietary source of HMB for obtaining pharmacologically active concentrations of the compound in blood plasma. In a study where participants consumed 2.42 grams of pure while fasting, the average plasma HMB concentration increased from a basal level of 5.1 to 408 μM after 30 minutes. At 150 minutes post-ingestion, the average plasma HMB concentration among participants was 275 μM. Abnormal HMB concentrations in urine and blood plasma have been noted in several disease states where it may serve as a diagnostic biomarker, particularly in the case of metabolic disorders. The following table lists some of these disorders along with the associated HMB concentrations detected in urine or blood plasma. History The first reported chemical synthesis of HMB was published in 1877 by the Russian chemists Michael and Alexander Zaytsev. HMB was isolated from the bark of Erythrophleum couminga (a Madagascan tree) in 1941 by Leopold Ružička. The earliest reported isolation of HMB as a human metabolite was by Tanaka