203126-83-4Relevant academic research and scientific papers
Synthesis of optically active bifunctional building blocks through enantioselective copper-catalyzed allylic alkylation using Grignard reagents
Van Zijl, Anthoni W.,Lopez, Fernando,Minnaard, Adriaan J.,Feringa, Ben L.
, p. 2558 - 2563 (2007/10/03)
Enantioselective copper-catalyzed allylic alkylations were performed on allylic bromides with a protected hydroxyl or amine functional group using several Grignard reagents and Taniaphos L1 as a ligand. The terminal olefin moiety in the products was transformed into various functional groups without racemization, providing facile access to a variety of versatile bifunctional chiral building blocks.
Rhodium-Catalyzed Methylenation of Aldehydes
Lebel, Helene,Paquet, Valerie
, p. 320 - 328 (2007/10/03)
The rhodium-catalyzed methylenation of aldehydes using trimethylsilyldiazomethane and triphenylphosphine produces a variety of terminal alkenes in excellent yields. These mild and nonbasic reaction conditions allow the conversion of enolizable substrates (keto aldehydes and nonracemic α-substituted aldehydes) to terminal alkenes without epimerization. Optimization of the reaction conditions led to the conclusion that a variety of rhodium(I) sources can be used as catalysts. The effect of the solvent on the reaction has also been studied, and it indicates that although the THF is the best solvent, other solvents may be used. The reactivity of the system is very much dependent on the nature of the phosphine reagent. The use of an easily removable phosphine is also described. Spectroscopic studies indicate that the reaction proceeds via an unusual mechanism which leads to the in situ formation of the salt-free phosphorus ylide, methylenetriphenylphosphorane.
Systematic studies on synthesis, structural elucidation, and biological evaluation of A-ring diastereomers of 2-methyl-1α,25-dihydroxyvitamin D3 and 20-epi-2-methyl-1α,25-dihydroxyvitamin D3
Takayama, Hiroaki,Konno, Katsuhiro,Fujishima, Toshie,Maki, Shojiro,Liu, Zhaopeng,Miura, Daishiro,Chokki, Manabu,Ishizuka, Seiichi,Smith, Connie,DeLuca, Hector F.,Nakagawa, Kimie,Kurobe, Mayuko,Okano, Toshio
, p. 277 - 285 (2007/10/03)
All possible A-ring diastereomers of 2-methyl-1α,25-dihydroxyvitamin D3 (2) and 20-epi-2-methyl-1α,25-dihydroxyvitamin D3 (3) were synthesized by palladium-catalyzed coupling reaction of A-ring 'enyne' synthons with CD-ring portions. The A-ring synthons were rationally synthesized via a novel and practical route, starting with methyl (R)-(+)- and (S)-(-)-3-hydroxy-2-methyl-propionate, in good yields. X-ray crystallographic analysis of 2α-methyl-1α,25-dihydroxyvitamin D3 (2b) and conformational analysis of the A-ring of 2α-methyl-(2b) and 2β-methyl-1α,25-dihydroxyvitamin D3 (2f) were carried out, and the results are described. All A-ring diastereomers (2 and 3), thus synthesized, were biologically evaluated both in vitro and in vivo. The biologic potency was highly dependent on the stereochemistry of the A-ring substituents. In particular, 2b showed 4-fold higher vitamin D receptor [VDR] binding activity than the natural hormone, and its 20-epimer (3b) exhibited exceptionally high activity, 12-fold more potent in VDR binding, 7-fold in calcium mobilization, and 590-fold in induction of human promyelocytic leukemia (HL-60) cell differentiation as compared with the natural hormone. Further, the 20-epi-2β-Me-1β, 3α(OH)2 isomer (3g) had significant biologic potencies compared to the natural hormone despite having 1β-OH configuration. The transcriptional activities on human osteocalcin gene promoter, including VDRE in transfected mammalian cells, were also evaluated. Finally, there was a clear contrast between the effects of the 2-methyl group on the HL-60 cell differentiation- and apoptosis-inducing activities of 2 and 3. Copyright
Synthesis, biological evaluation, and conformational analysis of A-ring diastereomers of 2-methyl-1,25-dihydroxyvitamin D3 and their 20-epimers: Unique activity profiles depending on the stereochemistry of the A-ring and at C-20
Konno,Fujishima,Maki,Liu,Miura,Chokki,Ishizuka,Yamaguchi,Kan,Kurihara,Miyata,Smith,DeLuca,Takayama
, p. 4247 - 4265 (2007/10/03)
All eight possible A-ring diastereomers of 2-methyl-1,25-dihydroxyvitamin D3 (2) and 2-methyl-20-epi-1,25-dihydroxyvitamin D3 (3) were convergently synthesized. The A-ring enyne synthons 19 were synthesized starting with methyl (S)-(
VITAMIN D3 DERIVATIVES AND PROCESS FOR PRODUCING THE SAME
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, (2008/06/13)
Provided are 1, 25-dihydroxy-2-methylvitamin D3 derivatives expressed by the general formula (I), [wherein each of R1and R2is independently a hydrogen atom or a tri(C1to C7alkyl)silyl group; herein configuration
A novel and practical route to A-ring enyne synthon for 1α,25-dihydroxyvitamin D3 analogs: Synthesis of A-ring diastereomert of 1α,25-dihydroxyvitamin D3 and 2-methyl-1,25-dihydroxyvitamin D3
Konno, Katsuhiro,Maki, Shojiro,Fujishima, Toshie,Zhaopeng, Liu,Miura, Daishiro,Chokki, Manabu,Takayama, Hiroaki
, p. 151 - 156 (2007/10/03)
A novel and practical route to the A-ring enyne synthon (2), which can be versatile far a variety of A-ring analogs of 1α,25-dihydroxyvitamin D3 (1), was developed. This novel method led to an improved synthesis of the A-ring diastereomers of 1, the compounds 13-15, and synthesis of the new analogs, 2-methyl-1,25-dihydroxyvitamin D3 (4) with its all possible diastereomers. The biological evaluation of the 2-methyl analogs showed the ααβ-isomer to be more potent than 1.
Absolute stereostructure of callystatin A, a potent cytotoxic polyketide from the marine sponge, Callyspongia truncata
Murakami, Nobutoshi,Wang, Weiqi,Aoki, Masashi,Tsutsui, Yasuhiro,Higuchi, Kouichi,Aoki, Shunji,Kobayashi, Motomasa
, p. 5533 - 5536 (2007/10/03)
The unidentified configurations at C5 and C10 incallystatin A (1), a potent cytotoxic polyketide from the marine sponge Callyspongia truncata, were determined to be R,R by comparing the circular dichroism spectrum of 1 with those of two model compounds 2 and 3. Compounds 2 and 3 were synthesized by using E-selective Wittig olefination at the C6-C7 position as a key reaction.
