Stereochemistry of 25‐hydroxyvitamin D₃—26,23‐lactone and 1α,25—dihydroxyvitamin D₃—26,23‐lactone in rat serum

Metabolic pathway to 25‐hydroxyvitamin D3‐26,23‐lactone from 25‐hydroxyvitamin D3

“…The 25-OHDs-26,23-lactone from 25-OH-D% 23,25-(OH)*Ds and 23,25,26-(OH)3D3 was identified by ultraviolet absorption, mass spectra and Fourier transform infrared spectra as in [5]. Table 1 shows that the production of 25-OH-D3-26,23-lactone from chick kidney homogenates incubated with 8 ,ug various vitamin D3 metabolites.…”

“…The synthesis of 25-OH-Da, 24,25_dihydroxyvita-min Ds (24,25-(OH)aDa), lcr,25-dihydroxyvitamin Ds (lcr,25-(OH),Ds) and 25,26-(OH)2D3 were done in our laboratory as in [ 11,12].25-OH-Da-26,23-Lactone, 23,25-(OIQ2Ds and 23,25,26(OH)aDa were isolated from the serum of rats given large doses of vitamin Ds as in [ 5,8,9]. Four possible diastereoisomers of 25.OH-Da-26,23-lactone were synthesized asm [5].…”

“…Four possible diastereoisomers of 25.OH-Da-26,23-lactone were synthesized asm [5]. Vitamin Da was obtained from Sigma Chemical Co. (Chicago IL).…”

“…A new metabolite of vitamin Da has been isolated from the plasma of chickens, rats and pigs and identified as 25hydroxyvitamin Da-26,231actone (25OH-Ds-26,23Jactone) [l-3]. The stereochemical configurations of natural 25OH-Da-26,23-lactone at the C-23 and C-25 positions were determined to be 23(S) and 25(R), respectively [4,5]. In [6] 25(5)26-dihydroxy vitamin Da (25@)26-(0H),Da) was reported as an intermediate in the biosynthesis of the 25-OH-D,-26, 23-lactone.…”

C-3 Epimerization of Vitamin D3 Metabolites and Further Metabolism of C-3 Epimers

“…The C-24 oxidation pathway, initiated by C-24 hydroxylation, leads to the conversion of 1␣,25(OH) 2 D 3 into a side chain cleavage product, calcitroic acid (4,5). The C-23 oxidation pathway, initiated by C-23 hydroxylation, leads to the formation of 1␣,25(OH) 2 D 3 -26,23-lactone (7)(8)(9)(10). The newly discovered C-3 epimerization pathway leads to the conversion of the configuration of the hydroxyl group at C-3 of the A-ring and produces 3-epi-1␣,25(OH) 2 D 3 from 1␣,25 (OH) 2 D 3 .…”