Showing papers by "Kazuo Nagasawa published in 2006"
TL;DR: In this paper, a highly enantio- and diastereoselective Henry reaction of various aldehydes with nitroethane was developed using the guanidine-thiourea bifunctional catalyst 1 (syn selectivity of 86:14 to 99:1 with 84−99% ee).
139 citations
TL;DR: A practical synthetic route to novel vitamin D antagonists of DLAM was developed from vitamin D(2) via the 1,3-dipolar cycloaddition reaction as a key step, and (23S,25S)-DLAM isomers bound effectively to VDRs and showed antagonistic activity in the HL-60 cell differentiation inhibition assay.
Abstract: A practical synthetic route to novel vitamin D antagonists of DLAM (1alpha,25-dihydroxyvitamin D(3)-26,23-lactam) was developed from vitamin D(2) via the 1,3-dipolar cycloaddition reaction as a key step. Six DLAM derivatives (24 compounds) with a variety of nitrogen substituents and stereochemistries at C23 and C25 were synthesized. Among these new derivatives, (23S,25S)-DLAM isomers bound effectively to VDRs and showed antagonistic activity in the HL-60 cell differentiation inhibition assay. The importance of the substituent on the nitrogen of DLAMs for antagonistic activity was also suggested by computational docking studies.
41 citations
TL;DR: In this paper, the authors designed and synthesized Telomestatin derivatives of 2a-2c, which have macrocyclic bisamide structure, and showed inhibitory activity of telomerase with an IC 50 of 2 μM.
Abstract: Telomestatin derivatives of 2a-2c, which have macrocyclic bisamide structure, were designed and synthesized. One of these compounds (2a) showed inhibitory activity of telomerase with an IC 50 of 2 μM.
37 citations
TL;DR: Metabolic activation of pivaloyl analogs in HL-60 cells was found to be necessary for binding to nuclear vitamin D(3) receptor (VDR) and nuclear androgen receptor (AR) binding activity.
36 citations
TL;DR: Novel, potent farnesoid X receptor (FXR) and peroxisome proliferator-activated receptor alpha (PPARalpha) agonists were obtained by using a diphenylmethane skeleton as a substitute for a steroid skeleton.
32 citations
TL;DR: In this article, a silicon nitride film was etched along boundary lines between discharge electrodes covered with a dielectric layer and the film, and a high etching rate more than 150 nm/min could be obtained.
Abstract: A new etching technique, which is useful for the formation of electrode grooves for finger and busber electrodes on solar cells, was examined using a surface discharge at atmospheric pressure. A silicon nitride film was etched along boundary lines between discharge electrodes covered with a dielectric layer and the film. It was found that intensive surface streamers play an essential role in the etching of the film and that a high etching rate more than 150 nm/min could be obtained.
10 citations
TL;DR: In this article, mild and neutral conditions of m-CPBA-induced regioselective ring opening reaction of isoxazolidine into ketonitrone were described.
Abstract: Mild and neutral conditions of m-CPBA-induced regioselective ring opening reaction of isoxazolidine into ketonitrone was described.
6 citations
TL;DR: In this paper, a highly diastereoselective version of the Henry reaction was developed using guanidine-thiourea bifunctional catalyst, which achieved a ratio of 84:16 to 99:1 for α-substituted aldehydes with nitromethane.
Abstract: A highly diastereoselective Henry reaction (diastereomer ratio of 84:16 to 99:1) of α-substituted aldehydes with nitromethane was developed using guanidine-thiourea bifunctional catalyst 1. N,N-Dibenzyl-protected α-amino aldehydes (2a, 2d-h) and α-hydroxy aldehydes protected as silyl ethers (2i-j) were suitable substrates. The matched combination of this catalytic system, i.e., S-aldehydes and (R,R)-1 catalyst, can be understood in terms of the transition state of the asymmetric version of the Henry reaction catalyzed by 1.
4 citations
3 citations
TL;DR: In this paper, a highly diastereoselective version of the Henry reaction was developed using guanidine-thiourea bifunctional catalyst, which achieved a ratio of 84:16 to 99:1 for α-substituted aldehydes with nitromethane.
Abstract: A highly diastereoselective Henry reaction (diastereomer ratio of 84:16 to 99:1) of α-substituted aldehydes with nitromethane was developed using guanidine-thiourea bifunctional catalyst 1. N,N-Dibenzyl-protected α-amino aldehydes (2a, 2d-h) and α-hydroxy aldehydes protected as silyl ethers (2i-j) were suitable substrates. The matched combination of this catalytic system, i.e., S-aldehydes and (R,R)-1 catalyst, can be understood in terms of the transition state of the asymmetric version of the Henry reaction catalyzed by 1.
3 citations
TL;DR: In this article, a highly enantio- and diastereoselective Henry reaction of various aldehydes with nitroethane was developed using the guanidine-thiourea bifunctional catalyst 1 (syn selectivity of 86:14 to 99:1 with 84−99% ee).
Abstract: A highly enantio- and diastereoselective Henry reaction of various aldehydes with nitroethane was developed using the guanidine-thiourea bifunctional catalyst 1 (syn selectivity of 86:14 to 99:1 with 84–99 % ee). A variety of nitroalkanes was treated with unbranched and branched aldehydes and gave nitro alcohols with high syn diastereoselectivities (90:10 to 99:1) and high enantioselectivities (85–95 % ee). This reaction was successfully utilized in a straightforward synthesis of (4S,5R)-epi-cytoxazone.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
TL;DR: The asymmetric total synthesis of batzelladine A (1) and B (2) has been achieved in this article by means of successive 1,3-dipolar cycloaddition reaction and subsequent cyclization, and direct esterification of the bicyclic carboxylic acid 35 with the guanidine alcohol 8 or 59 to construct the whole carbon skeleton of BAs.
Abstract: Asymmetric total synthesis of batzelladine A (1) and batzelladine D (2) has been achieved. Our synthesis of batzelladines features 1) stereoselective construction of the cyclic guanidine system by means of successive 1,3-dipolar cycloaddition reaction and subsequent cyclization, 2) direct esterification of the bicyclic carboxylic acid 35 with the guanidine alcohol 8 or 59 to construct the whole carbon skeleton of batzelladines, and 3) one-step formation of the alpha,beta-unsaturated aldehyde 53 from the primary alcohol 47 with tetra-n-propylammoniumperruthenate (TPAP), providing an efficient route to the left-hand bicyclic guanidine alcohol of batzelladine A (1). With the synthetic compounds 1 and 2 in hand, their target protein was examined by using immobilized CD4 and gp120 affinity gels. The results indicated that batzelladines A (1) and D (2) bind specifically to CD4.