Genzoh Tanabe

Di-tert-butylsilylene (DTBS) group-directed α-selective galactosylation unaffected by C-2 participating functionalities

We have discovered an unusual α-galactosylation using phenylthioglycoside of 4,6-O-di-tert-butylsilylene (DTBS)-protected galactose derivatives as a glycosyl donor, which was not hampered by the neighboring participation of C-2 acyl functionality such as NTroc and OBz. The power of the DTBS effect has been exemplified by the coupling reaction with various glycosyl acceptors.

Salaprinol and ponkoranol with thiosugar sulfonium sulfate structure from Salacia prinoides and α-glucosidase inhibitory activity of ponkoranol and kotalanol desulfate

The methanolic extract from the roots and stems of Indian Salacia prinoides and its water-eluted fraction of Diaion HP-20 column were found to exhibit inhibitory activities against α-glucosidase. From the water-eluted fraction, two new unique constituents with thiosugar sulfonium sulfate, salaprinol (1) and ponkoranol (2), were isolated together with 10 known constituents including salacinol and kotalanol. The structures of 1 and 2 were elucidated on the basis of chemical and physicochemical evidence. Furthermore, ponkoranol (2) and kotalanol desulfate (14) were found to show potent inhibitory activities against α-glucosidase.

Absolute stereostructures of novel norcadinane- and trinoreudesmane-type sesquiterpenes with nitric oxide production inhibitory activity from Alpinia oxyphylla

Novel 14-norcadinane-type sesquiterpenes, oxyphyllenodiols A and B, and 11,12,13-trinoreudesmane-type sesquiterpenes, oxyphyllenones A and B, were isolated from the methanolic extract of kernels of Alpinia oxyphylla. The absolute stereostructures of these norsesquiterpenes were determined on the basis of physicochemical and chemical evidence. In addition, oxyphyllenodiol A and oxyphyllenone A were found to inhibit the NO production in lipopolysaccharide-activated macrophages.

Clostridium scindens: a human gut microbe with a high potential to convert glucocorticoids into androgens

Clostridium scindens American Type Culture Collection 35704 is capable of converting primary bile acids to toxic secondary bile acids, as well as converting glucocorticoids to androgens by side-chain cleavage. The molecular structure of the side-chain cleavage product of cortisol produced by C. scindens was determined to be 11β-hydroxyandrost-4-ene-3,17-dione (11β-OHA) by high-resolution mass spectrometry, 1H and 13C NMR spectroscopy, and X-ray crystallography. Using RNA-Seq technology, we identified a cortisol-inducible (∼1,000-fold) operon (desABCD) encoding at least one enzyme involved in anaerobic side-chain cleavage. The desC gene was cloned, overexpressed, purified, and found to encode a 20α-hydroxysteroid dehydrogenase (HSDH). This operon also encodes a putative “transketolase” (desAB) hypothesized to have steroid-17,20-desmolase/oxidase activity, and a possible corticosteroid transporter (desD). RNA-Seq data suggests that the two-carbon side chain of glucocorticords may feed into the pentose-phosphate pathway and are used as a carbon source. The 20α-HSDH is hypothesized to function as a metabolic “rheostat” controlling rates of side-chain cleavage. Phylogenetic analysis suggests this operon is rare in nature and the desC gene evolved from a gene encoding threonine dehydrogenase. The physiological effect of 11β-OHAD on the host or other gut microbes is currently unknown.

Reexamination of Products and the Reaction Mechanism of the Chalcogeno-Baylis–Hillman Reaction: Chalcogenide–TiCl4-mediated Reactions of Electron-Deficient Alkenes with Aldehydes

Abstract Reactions of p -nitrobenzaldehyde ( 4 ) with methyl vinyl ketone ( 5 ) were conducted in the presence of TiCl 4 and dimethyl sulfide ( 3 ) or selenopyranone 6 . When the raw product was purified by column chromatography on silica gel, α-chloromethyl aldol 8 was obtained as a mixture of diastereoisomers 8a and 8b . In contrast, purification of the raw product by preparative TLC on silica gel gave α-methylene aldol 7 . The mechanism for the formation of α-chloromethyl aldol 8 and diasteroselection for the syn -isomer 8a and anti -isomer 8b are discussed.

Alpha-sulfanyl and alpha-selanyl propadienyl cations: regioselective generations and cycloadditions with thioamides and selemides controlled by MeNO2-H2O system.

Alpha-sulfanyl and alpha-selanyl propadienyl cations were easily generated by the catalytic system, scandium triflate-nitromethane-H(2)O in the presence of Bu(4)NHSO(4), to regioselectively afford the multifunctionalized thiazoles and selenazoles in high yields.

Facile synthesis of de-O-sulfated salacinols: Revision of the structure of neosalacinol, a potent α-glucosidase inhibitor

Facile synthesis of de-O-sulfated salacinols (3) was developed by employing the coupling reaction of an epoxide, 1,2-anhydro-3,4-di-O-benzyl-D-erythritol (9) with 2,3,5-tri-O-benzyl-1,4-dideoxy-1,4-epithio-D-arabinitol (10) as the key reaction. The reported structure of a potent alpha-glucosidase inhibitor named neosalacinol (8), isolated recently from Ayurvedic medicine Salacia oblonga, was proved incorrect, and revised to be de-O-sulfated salacinol formate (3c) by comparison of the spectroscopic properties with those of the authentic specimen synthesized. Discrepancies and confusion in the literature concerning the NMR spectroscopic properties of salacinol (1) have also been clarified.

A regioselective addition reaction of a sulfonyl radical to conjugate enynesulfones: A convenient synthesis of 1,4-bis(arylsulfonyl)-1,3-butadiene

Abstract p -Tolyl benzeneselenosulfonate regioselectively added to the conjugate enynesulfones 1–9 gave (1 E ,3 E )-1,4-bis(arylsulfonyl)-1,3-butadienes 10–17 , which were converted to the 4-hetero atom-substituted-1-phenylsulfonyl-1,3-butadienes 18, 21 and 22 .

Docking and SAR studies of salacinol derivatives as α-glucosidase inhibitors

Salacinol is a potent alpha-glucosidase inhibitor isolated from Salacia reticulata, and a good lead compound for an antidiabetic drug. It is essential to clarify the binding state of salacinol to alpha-glucosidase for efficient optimization study using structure-based drug design. Redocking simulations of two inhibitors, acarbose and casuarine whose complex structures are known, were performed to assure the appropriate docking pose prediction. The simulation reproduced both experimental binding states with accuracy. Then, using the same simulation protocol, the binding mode of salacinol and its derivatives has been predicted. Salacinol bound to the protein with a similar binding mode as casuarine, and the predicted structures could explain most of the structure-activity relationships of salacinol derivatives.

A concise construction of an erythrinane skeleton using Mn(III)/Cu(II)-mediated oxidative radical cyclization of α-methylthio amides

Oxidative radical cyclizations of enamide 3 with Mn(OAc)3 in the presence of Cu(II) were examined. When Cu(OAc)2 was used as an additive, 4-acetoxyerythrinane derivative 5 was formed, whereas the use of Cu(OTf)2 afforded simple erythrinane 6.