Cyclopentane and Cyclobutane Derivatives

1 Cyclopentane and Cydobutane Derivatives. - A review of applications and mechanistic aspects of the CpiZr induced direct ring contraction of hept-6-enose and hex-5-enose derivatives to cyclopentane and cyclobutane ring systems with emphasis on the application to oxetanocin synthesis has appeared. (See also Vol. 

Reagents i, Swem oxidation (modified) ii, Sml2, Bu OH, HMPA 

Cyclopentane rings can also be formed readily by treating 6-deoxy-6-nitro-D-fructose (prepared enzymatically from dihydroacetone phosphate and 3-deoxy-3-nitro-D,L-glyceraldehyde in the presence of an aldolase then phosphatase) with acetic anhydride and boron trifluoride etherate, then subjecting the mixture to chromatography on silica gel thereby affording 63 and the epimer at the indicated carbon atom.  

A non-carbohydrate route starting from a cyclopentanone has been developed to prepare the carbocyclic analogue of ascorbic and isoascorbic acid, and all possible carbapentofuranoses have been synthesized from norbom-5-en-2-one (optically pure).  

Cyclopentane rings as found in mannostatins, trehazoline, aristeromycin, allosamizoline and derivatives are covered in Chapter 19. 

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Cyclopentane and Cyclobutane Derivatives.-The isolation of the unsaturated cyclitol 59 from Streptomyces citricolor has been described and proposed as a biosynthetic precursor of aristeromycin and neplanocin A. 

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