163011-08-3Relevant articles and documents
Syntheses of 1-alkyl-1,25-dihydroxyvitamin D3
Ishida,Shimizu,Yamamoto,Iwasaki,Yamada,Yamaguchi
, p. 1828 - 1833 (1995)
1-Alkylated analogs of 1α,25-(OH)2D3 were synthesized to investigate the effect of the alkyl group on the A-ring conformation and the biological potency. The analogs were synthesized via two routes. In the first approach, alkylation of 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) adduct of 1-oxoprovitamin D (4) was used as the key step to synthesize 1β-methyl-1α,25-dihydroxyprovitamin D3 (OH)2D3 (16a) efficiently and stereoselectively. The photolysis of the provitamin D (16a), however, gave the desired previtamin D (17a) only as a minor product (2D3 were synthesized conveniently from 25-hydroxy-1-oxoprevitamin D3 (19) by reaction with an alkyllithium ollowed by thermal isomerization. In the alkylation, the alkyllithium attacked the ketone preferentially from the side of the 3β-hydroxyl group to afford the 1β-alkyl-1α-hydroxy epimer in a 1.6-2.7 to 1 ratio over the 1α-alkyl-1β-hydroxy isomer. Introduction of a 1β-methyl group to 1α,25-(OH)2D3, shifted the equilibrium between the two chair conformations of the A-ring preferentially to the side of the α-form (4:1) and reduced considerably the activity to bind to the VDR.
New Photoisomerization of Provitamin D caused by Hydroxylation at C(1)
Yamada, Sachiko,Ishizaka, Hironobu,Ishida, Hiroki,Yamamoto, Keiko
, p. 423 - 424 (2007/10/02)
1α-Hydroxyprovitamin D is found to undergo a new photochemical isomerization cascade initiated by the 1,10-bond cleavage in addition to the normal electrocyclic B-ring opening and this new isomerization becomes the major pathway when a methyl group is pre
