1α,25-(OH)(2)-9α-Methylvitamin D(3) (4), the first known analogue of the natural hormone 1α,25-(OH)(2)D(3) (3) with an alkyl substituent at C-9, and two 1α,25-(OH)(2)-9-methylene-10,19-dihydrovitamin D(3) analogues (7 and 8) with an unprecedented non-natural triene system were synthesized by thermal isomerization of 1α,25-(OH)(2)-9-methylprevitamin D(3) (6). Three alternative approaches (Sonogashira, Stille, or stereoselective dehydration of a tertiary propargyl alcohol) have been successfully used to construct the dienyne precursors of previtamin 6 possessing two methyl groups capable of participating in the [1,7]-sigmatropic hydrogen shift.

Many plant species can reproduce by both sexual and vegetative means. Clonal diversity and degree of intermingling of clones in the vegetative reproductive mode can influence the mating and fertility of individuals. The aim of the study was to assess the clonal structure and its potential influence on gene flow and generative reproduction efficiency in six endangered Betula humilis populations from the southwestern margin of the species range. Analyses of seven microsatellite loci revealed 86 genets among 522 samples. In general, the phalanx strategy dominated in the populations considered, as 76% of ramets shared the same genotype with their closest neighbour. Nevertheless, substantial clonal and genetic diversities and high contribution of unrelated individuals in all B. humilis stands suggest that panmictic pollination prevails. On the other hand, positive and significant relationships between genetic and geographic distances in the two populations could be a consequence of biparental inbreeding resulting from the pollen and seed flow limitations. The seed germination capacity was very low (2.70%); however, the populations characterised by the lowest and highest values of clonal diversity parameters did not differ significantly in the number of germinated seeds, which indicates that clonality is not responsible for seed production failure.

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Continuing the structure-activity relationship studies in the vitamin D area, we designed and synthesized novel C-9 substituted calcitriol analogues, possessing different nonpolar groups at this position. 9α-Methyl-1α,25-(OH)2D3, both epimers of 9-methylene-10,19-dihydro-1α,25-(OH)2D3 as well as the parent vitamin with the "reversed" triene system, 9-methylene-19-nor-1α,25-(OH)2D3, were obtained from the previtamin D precursors, constructed by either Suzuki-Miyaura, Sonogashira, or Stille couplings of the corresponding A- and C,D-ring fragments. An alternative synthetic path, leading to the latter vitamin and its homologue with 9-ethylidene group, involved formation of dienynes as precursors of the respective 19-norprevitamin D compounds. 9β-Methyl-19-nor-1α,25-(OH)2D3 was prepared by homogeneous hydrogenation with Wilkinson catalyst, and this analogue was found to be the most active in vitro. Moreover, 9α-methyl-1α,25-(OH)2D3 and 9-methylene-19-nor-1α,25-(OH)2D3 showed some in vitro activity, however, the in vivo assays indicated only weak calcemic potency of these compounds in the intestinal calcium transport.

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