- Cis Selective RCM Study to the 14-Membered Cyclic Subunit of Bielschowskysin
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A concise, (Z)-selective ring-closing metathesis (RCM) route to the 14-membered carbocycle of bielschowskysin is detailed using naturally occurring chiral starting materials. Unproductive RCM substrates were attributed to alkyne chelation of the ruthenium catalyst and steric disadvantages within the cembranoid precursors, which was eventually circumvented by using cyclic diol benzylidene protection involving a C8-quaternary carbinol center.
- Gramani, Subramanian G.,Sriramula, Ravi K.,Sekar, Karthik,Yang, Eugene G.,Battu, Praveena,Kopecky, A?cha,Lear, Martin J.
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Read Online
- A method for preparation of a purine derivative and intermediates
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The invention discloses a preparation method and intermediates of purine derivatives. According to the preparation method, a compound II and a compound III have a coupling reaction in an organic solvent under the actions of alkali and palladium catalysts to prepare the purine derivatives. Compared with the prior art, the raw materials used in the preparation method are cheap and common, and the preparation method is simple and efficient, is suitable for industrial production and provides a new way for the synthesis of entecavir drugs.
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Paragraph 0121-0123
(2016/12/01)
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- 13-Step total synthesis of Dendrodolide K following iterative Bartlett-Smith iodocarbonate cyclization
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A convergent total synthesis of Dendrodolide K has been achieved starting from commercially available homoallyl alcohol 17 in 13 longest linear sequence with 18.2% overall yield. The key features of this synthesis are Bartlett-Smith iodocarbonate cyclizat
- Mohapatra, Debendra K.,Pulluri, Karthik,Gajula, Srinivas,Yadav, Jhillu S.
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supporting information
p. 6377 - 6380
(2015/11/16)
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- Diastereoselective iodocarbocyclization reaction of 2- or 3-oxy-4-pentenylmalonate derivatives
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1,2- Or 1,3-asymmetric induction in the iodocarbocyclization reaction of 4-pentenylmalonate derivatives having a stereogenic center at an allylic or a homoallylic position has been investigated. The iodocarbocyclization reactions of 3-oxy-4-pentenylmalonate derivatives proceeded with high cis-selectivity through stereoelectronic control of the oxygenated substituent at an allylic position. In the reaction of (S)-2-siloxy-4-pentenylmalonate, an excellent diastereoselectivity was achieved through the utilization of double stereodifferentiation with a chiral titanium catalyst. Furthermore, as an application of the present reaction, the asymmetric syntheses of cyclosarkomycin and a synthetic intermediate of brefeldin A from optically pure 2- and 3-oxy-4-pentenylmalonate derivatives are also described.
- Inoue, Tadashi,Kitagawa, Osamu,Oda, Yoko,Taguchi, Takeo
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p. 8256 - 8263
(2007/10/03)
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