Shimizu 2 Cyclization

Recently, Shimizu reported a novel polar cycloaddition of a 1,2-thiazinylium salt <99TL95>. Compound 175 was generated in situ from the reaction of compound 165 with trifluoroacetic anhydride and lithium tetrafluoroborate. It can undergo a cyclization reaction... 

Independently, Prasad and Shimizu (24) as well as Lee et al. (25) proposed that brevetoxin A is biosynthesized from the cyclization of a polyepoxide precursor in a series of Sn2 R,R)-trans epoxide openings (Fig. 4c). Galfimore and Spencer (3) argue that the nine disfavored endo-tet closures required for this mechanism makes it mechanistically unlikely and point out that an alternative cascade of Sn2 epoxide openings in the opposite direction from all (S,S)-trans epoxides yields the same structure. 

Kuroda, C., Shimizu, S., and Satoh, J.Y, A short-step synthesis of 14,15-dinoreudesmanolides using intramolecular cyclization of an allylsilane, 7. Chem. Soc., Perkin Trans. 1, 519, 1990. 

Kuroda, C., Shimizu, S., Haishima, T., and Satoh, J.Y, Synthesis of a stereoisomer of frullanolide utilizing the intramolecular cyclization of co-formyl-2-alkenylsilane. Bull. Chem. Soc.. Jpn., 66, 2298, 1993. Kuroda, C., Inoue, S., Kato, S., and Satoh, J.Y, Synthesis of a-methylene-y-lactones fused to a perhydro azulene carbon framework through intramolecular cyclization of allylsilanes, 7. Chem. Res. (M), 458, 1993. 

Nagasawa, K., Zako, Y., Ishihara, H. and Shimizu, I. (1991) Stereoselective synthesis of la-hydrox5Tvitamin D3 A-ring synthons by palladium-catalyzed cyclization. Tetrahedron Lett., 32, 4937- 0. 

Lewis acid-promoted cyclization of 5-hexenals J. A. Marshall, Chemtracts-Org. Chem. 5, 1-7 (1992). Review of alkenes as enophiles B. B. Snider, Comp. Org. Syn. 5, 1-27 (1991). Review of carbonyl compounds as enophiles idem, ibid. 2, 527-561 in conjunction with asymmetric synthesis K. Mikami, M. Shimizu, Chem. Rev. 92,1021-1050 (1992) K. Mikami et al, Synlett 1992, 255-265. 

Fig. 3.5 Biosynthesis pathway of saxitoxin as proposed by Shimizu et al. [224]. The reaction steps are (1) Claisen-condensation between acetate and arginine (2) amidino transfer from a second arginine to the a-amino group of intermediate B (3) and (4), cyclization (5), introduction of S-adenosyl methionine (SAM) methyl-derived side chain, involving the loss of one methionine methyl hydride (6) 1,2-H shift (7) epoxidation of methylene side chain (8) opening of epoxide to an aldehyde (9) reduction of the aldehyde to hydroxyl (10) carbamoyl transfer and dihydroxylation of C-12...

Norris D, Chen P, Barrish JC, Jagabandhu D, Moquin R, Chen BC, Guo P (2001) Synthesis of imidazo[l,5-a]quinoxalin-4(57/)-one template via a novel intramolecular cyclization process. Tetrahedron Lett 42(26) 4297 299. doi 10.1016/S0040-4039(01)00698-0 Ohmori J, Shimizu-Sasamata M, Okada M, Sakamoto S (1997) 8-(lH-imidazol-l-yl)-7-nitro-4 (5H)-imidazo[l,2-a]quinoxalinone and related compounds synthesis and stiucture-acUvity relationships for the AMPA-type non-NMDA receptor. J Med Chem 40(13) 2053-2063. doi 10.1021/jm960664c... 

Ohshima T, Xu Y, Takita R, Shimizu S, Zhong D, Shibasaki M. Enantioselective total synthesis of (—)-strychnine using the catal3ftic asymmetric Michael reaction and tandem cyclization. J. Am. Chem. Soc. 2002 124(49) 14546-14547 (Erratum 2003 125(7) 2014). 

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