| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2005: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2004: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The following results have been achieved that aimed to the synthesis of organic compounds containing or using ring-flipped sugars.
(1) Investigation in the ring-conformation of glucose derivatives that possess two bulky silyl protecting groups.
The ring conformations of glucopyranoses bearing two bulky silyl protecting group at the 3-and 4-0 positions were investigated. Observations showed that the introduction of the two TBDPS groups can flip the pyranose-ring into the 1C4 conformation possessing more axial substituents. On the other hand, the pyranose rings of the 2,3-bis-O-TBDPS-of TBS-analogues were in the 1C4 form. These findings indicate that the introduction of bulky silyl protecting groups at the 2-and 3-positions can also flip a pyranose ring.
(2) Ring conformations of the cyclohexane derivatives possessing bulky siloxy groups.
The rings of the (±)-trans-1,2-bis-(R3SiO)cyclohexanes prefer the diaxial chair conformation in the crystal state. Further, the introduction of the bulky s
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ilyl groups into vicinal trans-hydroxy groups induced a flip of rings of myo-inositol derivatives from the equatorial-rich chair form into the axial-rich one.
(3) Beta-selective O-glucosidation using twist-boat glucosyl donors
Ethyl 6-0-pivaloyl-1-thio-2,3,4-tris-0-triisopropylsilyl-D-glucopyranoside induced highly beta-selective O-glucosidations. The selectivity would be caused by the twist-boat conformation of the pyranose.
(4) Synthetic approach to an ellagitannin containing a flipped sugar
The synthesis of nonamethylcorilagin is achieved. This synthesis demonstrates the first synthetic approach to a 3,6-bridged ellagitannin skeleton whose conformation of the D-glucose core is 1C4 or skew boat.
(5) Facile synthesis of partly O-benzylated glucose derivatives
Full-O-benzylated methyl-alfa-D-glucopyranoside shows a steady order in the stepwise debenzylation when it is treated with sulfuric acid in acetic anhydride. Based on the order of the debenzylation, the regioselective preparations of 2,3,4-tri-, 2,3-, 2,4-, 3,4-di-, and 2-mono-O-benzylated D-glucopyranose acetates were facilitated. Less
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