Yamamoto’s synthesis

Scheme 35 Sequential formation of rings I and H by intramolecular allylation/RCM in Yamamoto s synthesis of the F-K ring segment 186 of brevetoxin B (184) [91]...

Scheme 27 summarizes Yamamoto s synthesis of lardolure (16), the aggregation pheromone of the acarid mite, Lardoglyphus konoi [45]. The key-step was the transformation of acetal A to hemiacetal B. 

RCM was also used in Yamamoto s synthesis of the marine neurotoxin gambierol to close the... 

At the exotic end of the Lewis acid scale is tetrafluorosilane (mp -90 5C, bp -86 UC) first proposed by Corey and Yi as a mild and selective reagent for the cleavage of silyl-protected alcohols with the reactivity order being EtiSi > f-Bu-Me2Si f-BuPhiSi/ 1 The substrate in dichloromethane or acetonitrile, is stirred at room temperature under an atmosphere of excess tetrafluorosilane provided by a gas-filled balloon. The reaction is slow in dichloromethane but quite fast (ca. 15 min) in acetonitrile. In the final step of Yamamoto s synthesis of the Hemibrevetoxin B [Scheme 4.40]61 the secondary TIPS and TBS ethers were removed from 40.1 with tetrafluorosilane. Identical conditions were used by Nicolaou et al to remove two TBS ethers in the final step of their synthesis of Hemibrevetoxin B.62 In the example shown in Scheme 4,41, deprotection with fluoride (basic) or cerium(lV) ammonium nitrate (CAN) in methanol (neutral) isomerised the angelate to the more thermodynamically stable tiglate.63 However, with tetrafluorosilane, no isomerisation occurred during the deprotection step. 

RCM was also used in Yamamoto s total synthesis of the marine neurotoxin gambierol (81) [62], to close the central seven-membered E ring, thereby completing the octacyclic polyether core 80 (Scheme 15). Following previously developed methodology [63], metathesis precursor 79 was produced as the major epimer, by boron trifluoride etherate-mediated intramolecular allylation of a-chloroacetoxy ether 78. Subsequent treatment of 79 with catalyst C produced the octacyclic ether 80 in 88% yield. 

Scheme 15 Formation of the central rings D and E by sequential intramolecular allylation and RCM in Yamamoto s total synthesis of the marine neurotoxin gambierol (81) [62]...

S850 M. Yamamoto, S, Tanaka, K. Naruchi, and K. Yamada, Synthesis,... 

Takeuchi Y, Nagao Y, Toma K, Yoshikawa Y, AMyama T, Nishioka H, Abe H, Harayama T, Yamamoto S (1999) Synthesis and Siderophore Activity of Vibrioferrin and One of its Diastereomeric Isomers. Chem Pharm Bull 47 1284... 

F. Yamamoto, S. Sasaki, M. Maeda, Positron labeled antioxidants Synthesis and tissue biodistribution of 6-deoxy-6-[ F]fluoro-L-ascorbic acid, Appl. Radiat. Isot. 43 (1992) 633-639. 

Ishihara, K. Karumi, Y. Kondo, S. Yamamoto, H. Synthesis of C symmetric, optically active triamidoamine and protetraazaphos-phatrane. /. Org. Chem. 1998, 63, 5692-5695. 

Y. Yamamoto, S. G. Pyne, D. Schinzer, B. L. Feringa, J. F. G. A. Jansen, Formation of C-C Bonds by Reactions Involving Olefinic Double Bonds - Addition to a,/3-Unsaturated Carbonyl Compounds (Michael-Type Additions), in Methoden Org. Chem. (Houben-Weyl) 4th ed. 1952, Stereoselective Synthesis (G. Helmchen, R. W. Hoffmann, J. Mulzer, E. Schaumann, Eds.), Vol. E21b, 2041, Georg Thieme Verlag, Stuttgart, 1995. 

Diastereospecific reduction of an enone. A key step in a synthesis of the lichen macrolide (+ )-aspicilin (4) is the reduction of the oxodienelactone 2 to the dienol 3 with Yamamoto s reagent (1) in 96% yield. Dihydroxylation of 3 with 0s04 and pyridine followed by H,S reduction gives the triol (4) in 40% yield. 

Homoallylic alcohols can be asymmetrically epoxidized using a chiral vanadium catalyst equipped with the hydroxaraic acid ligand 45, as exemplified in Yamamoto s concise synthesis... 

Nemoto, H. Cai, J. Asao, N. Iwamoto, S. Yamamoto, Y. Synthesis and biological properties of water-soluble p-boronophenylalanine derivatives. Relationship between water solubility, cytotoxicity, and cellular uptake. J. Med. Chem. 1995, 38, 1673-1678. 

Scheme 5.2.26 Yamamoto s studies toward the synthesis of hemibrevetoxin...

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