Cyclopentane derivatives, synthesis

Chan T-H, Xin Y-C, von Itzstein M (1997) Synthesis of phosphonic add analogs of siaUc acids (Neu5Ac and KDN) as potential sialidase inhibitors. J Org Chem 62 3500-3504 Chand P, Kotian PL, Dehghani A, El-Kattan Y, Lin T-H, Hutchison TL, Babu YS, Bantia S, Elliott AJ, Montgomery JA (2001) Systematic structure-based design and stereoselective synthesis of novel multisubstituted cyclopentane derivatives with potent antiinfluenza activity. J Med Chem 44 4379 392... 

The procedure described here serves to illustrate a general [3+2] annulation method for the synthesis of cyclopentane derivatives. A unique feature of this one-step annulation is its capacity to generate regio-specifically five-raembered rings substituted at each position, functionally equipped for further synthetic elaboration. As formulated in the following equation, the reaction proceeds with remarkably high stereoselectivity via the effective suprafacial addition of the three-carbon allene component to an electron-deficient olefin ("allenophile"). ... 

Organometallic methods, with the possible exception of those involving the stoichiometric generation of enolates and other stabilized carbanionic species 140], have seldom been used in carbohydrate chemistry for the synthesis of cyclohexane and cyclopentane derivatives. The present discussion will not cover these areas. The earliest of the examples using a catalytic transition metal appears in the work of Trost and Runge [41], who reported the Pd-catalyzed transformation of the mannose-derived intermediate 22 to the functionalized cyclopentane 23 in 98% yield (Scheme 10). Under a different set of conditions, the same substrate gives a cycloheptenone 24. Other related reactions are the catalytic versions of the Ferrier protocol for the conversion of methylene sugars to cyclohexanones (see Chap. 26) [40,42,43]. 

The synthetic protocols used for the preparation of oligonucleotides on supports can also be used to prepare oligomers from diols other than nucleosides. Symmetric or unsymmetric diols, such as N-acylated 4-hydroxyprolinol [268] or cyclopentane-derived diols (carbocyclic deoxyribose analogs [269]), can be selectively mono-trity-lated and then converted into a phosphoramidite that is suitable for the solid-phase synthesis of oligophosphates. An illustrative synthesis of protected //-phosphonates from diols, as well as their conversion on CPG into oligomeric phosphoramidates, are outlined in Figure 16.28. 

Canadian workers have been exploring methods for the conversion of cheap and readily available camphor into enantiopure cyclopentane derivatives for use in terpene and steroid synthesis, e.g. 1 — 2. In a recent extension of these studies, em/o-3-bromo-4-methylcamphor 3 (0.1 mol) was... 

P. Chand, P. L. Kotian, A. Dehghani, Y. El-Kattan, T. H. Lin, T. L. Hutchison, Y. S. Babu, S. Bantia, A. J. Elliott, and J. A. Montgomery, Systematic structure-based design and stereoselective synthesis of novel multisubstituted cyclopentane derivatives with potent antiinfluenza activity, J. Med. Chem., 44 (2001) 4379-4392. 

Radical methods are useful for the synthesis of highly functionalized enantiomerically pure cyclopentane derivatives [95SL918]. Reductive cyclization of the arabinolactone 88 furnished the eir-lactone 89 in quantitative yield. Exhaustive reduction with borane-dimethylsulfide gave the functionalized cyclopentane 90. 

Dipolar cycloadditions, closely related to the Diels-Alder reaction,1,2 result in the synthesis of a five-membered adduct including cyclopentane derivatives.417"426... 

Homeman, A.M. et al. Stereoselective Radical Induced Cyclisation of Unsaturated Aldonolactones Synthesis of Highly Functionalized, Enantiomerically Pure Cyclopentane Derivatives. 2.1 1995 [124]... 

The lithiated sulfone 413 has been alkylated with alkyl bromides623 in the presence of HMPA and with 1,4-dihaloalkanes623,624, acting as an acyl dianion. For instance, treatment of intermediate 413 with the dimesylate 414625 has been applied to the synthesis of the cyclopentane derivative 415, a precursor in the synthesis of 3-oxocarbacyclins (Scheme 107)625. Compound 415 was hydrolyzed to the corresponding cyclopentenone with 50% sulfuric acid in ethanol. 

Taylor and Wei have also developed a versatile method for the synthesis of cyclopentanes employing readily available organolithium compounds as difunctional, conjunctive reagents. This strategy represents an anionic [3 + 2] approach to substituted cyclopentanes. The reactions of lithiated alkenes 149 with activated alkenes 150 afford cyclopentane derivatives 151 in reasonable yield and, in some cases, with excehent stereocontrol. The alkenes 150 must be added over extended times to minimize polymerization processes. The... 

A strategy for the synthesis of trehazolamine has been developed from 1-methox-yethoxymethyl-3-pivaloyloxymethylpyridinium perchlorate via amino cyclopentane derivatives (Schemes 42 and 43).115 Pyridinium salt 351 was prepared by a two-step sequence from 3-(hydrooxymethyl)pyridine 349 via 350 (Scheme 42). Irradiation of 351 in aqueous NaHC03 led to production of the separable bicyclic aziridines 352 (20%) and 353 (16%). Ring opening of 352 by acetic acid, followed by removal of the... 

TRANSITION METAL CATALYZED REACTIONS OF VINYLCYCLOPROPANES SYNTHESIS OF 1200 CYCLOPENTANE DERIVATIVES... 

It is well known that cyclobutanones can be transformed to cyclopentane derivatives directly with diazomethane or indirectly via the cyanohydrins218> 228), or with tris(phe-nylthio)methyllithium 219,220), but in many cases the reactions are not regioselective and lead to different regioisomers. Cyclobutyl ketones lead to substituted cyclopentanones in highly acidic media 226 and the synthesis of cyclopentanones from methylene-cyclobutanes requires a palladium catalyst 227). 

Synthesis of Bacillariolides I-III. Marine oxylipin bacillariolides I-III are synthesized from (ft1)-malic acid, using a common chiral cyclopentane derivative prepared as depicted in Eq. 145.252 Two consecutive alkylation reactions of lithioallyl sulfone are responsible for the generation of the cyclopentane intermediate. The synthetic route also includes a reductive desulfonylation with Na/Hg in MeOH/THF (Eq. 145). 

Another example using baker s yeast demonstrates the highly enantio- and diastcreoselective reduction of sulfur-functionalized 2-phcnylthio-2-cyclopentenone92. Optically active cyclopentane derivatives with multiple functionalization are useful starting materials for the synthesis of prostaglandins and related compounds. 

Abstraction at acetal centers. Simpkins used a hydrogen atom abstraction from tetrahydrofuranyl and tetrahydropyranyl acetals for the preparation of spiroketals (Scheme 41, Eq. 41.1)] [137]. Malacria has inserted this process in a cascade reaction leading to functionalized cyclopentanone (Eq. 41.2) [138], Bertrand and Crich applied this reaction for the preparation of optically active cyclopentane derivative under chiral auxiliary control (Eq. 41.3) [139]. The synthesis of anomeric spiro-nucleosides was reported independently by Chatgilialoglu [46] and Kittaka [140]. In the example reported in Eq. (41.4), the gem-dibromovinyl derivative was treated with hexabutyldistannane to afford the desired spiro derivatives. This kind of reac-... 

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