RESUMEN
A convergent synthesis has been developed for the preparation of solid-phase bound construct 1, consisting of an orthogonally protected trifunctional core structure that is attached to TentaGel via a photocleavable linker. [structure: see text]
RESUMEN
The synthesis of four CD-ring-modified 19-nor-1alpha, 25-dihydroxyvitamin D(3) derivatives lacking C15, referred to as 6C analogues, and diastereomeric at C17 and C20 is described. The synthesis involves an Ireland-Claisen rearrangement of a 3-methyl-substituted ester of (1R)-3-methyl-2-cyclohexen-1-ol as the key step, followed by elaboration of the side chain, transformation into a C8 cyclohexanone derivative, and final Wittig-Horner coupling with the 19-nor A-ring phosphine oxide. Despite possessing a more flexible side chain than the parent hormone, biological evaluation showed an unexpected superagonistic antiproliferative and prodifferentiating activity (10-50 times higher as compared to that of 1alpha,25(OH)(2)D(3)) for the diastereomer with the "natural" configuration at C17 and C20. The other diastereomers exhibit a 25-90% decrease in activity. All four analogues show a decreased binding affinity (45% or less), and their calcemic activity is 4-400 times less than that of 1alpha,25(OH)(2)D(3). The conformational behavior of their side chain was studied using molecular mechanics calculations, and the result is presented as volume maps. A relative activity volume was determined by subtraction of the volume map of the least active analogue from the volume map of the most active one. This shows three regions corresponding to preferred orientations in space of the side chain of the active analogue. One of these regions was found to overlap with the region that is preferentially occupied by the most active of the four diastereomeric 22-methyl-substituted 1alpha,25(OH)(2)D(3) analogues.
Asunto(s)
Vitamina D/análogos & derivados , Animales , Unión Competitiva , Diferenciación Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Humanos , Queratinocitos , Ratones , Modelos Moleculares , Conformación Molecular , Estructura Molecular , Receptores de Calcitriol/metabolismo , Estereoisomerismo , Porcinos , Células Tumorales Cultivadas , Vitamina D/químicaRESUMEN
Dot maps used to represent the calculated conformations of the side chain of vitamin D derivatives are improved by replacing dots by coloured balls to create volume maps and to identify particular energy windows. Two procedures to define a relative activity volume, based on a pair of analogs with distinctly different biological activity and conformational behaviour, are presented.