Cyclopentene 3,6-diacetoxy

Diacetates of 1,4-butenediol derivatives are useful for double allylation to give cyclic compounds. l,4-Diacetoxy-2-butene (126) reacts with the cyclohexanone enamine 125 to give bicyclo[4.3.1]decenone (127) and vinylbicy-clo[3.2.1]octanone (128)[85,86]. The reaction of the 3-ketoglutarate 130 with cij-cyclopentene-3,5-diacetate (129) affords the furan derivative 131 [87]. The C- and 0-allylations of ambident lithium [(phenylsulfonyl)methylene]nitronate (132) with 129 give isoxazoline-2-oxide 133, which is converted into c -3-hydroxy-4-cyanocyclopentene (134)[S8]. Similarly, chiral m-3-amino-4-hyd-roxycyclopentene was prepared by the cyclization of yV-tosylcarbamate[89]. 

The Bacillus subtilis lipase A (BSLA) was the subject of two short directed evolution studies [19,47]. In one case systematic saturation mutagenesis at all of the ISlpositions of BSLA was performed [19]. Using meso-l,4-diacetoxy-2-cyclopentene as the substrate, reversed enantioselectivity of up to 83% ee was observed. In another study synthetic shuffling (Assembly of Designed Oligonucleotides) was tested using BSLA [47]. 

The product, l,4-diacetoxy-2-allyl-3-methyl-2-cyclopentene, obtained (45% current efficiency) from 2-allyl-3-methyl-l,3-cyclopentadiene through anodic oxidation with carbon rod anode in acetic acid is successfully used as a starting compound in the synthesis of allethrolone as shown in equation 23. 

The Bacillus subtilis lipase A (BSLA) is an unusual lipase because it lacks the so-called lid structural unit 13(3). Moreover, it is a small enzyme composed of only 181 amino acids. The initial results of an ongoing study are remarkable and illustrate the power of directed evolution 45,137). The desymmetrization of meso-, 4-diacetoxy-2-cyclopentene (15) was chosen as the model reaction, and the MS-based ee assay using an appropriately Ds-labeled substrate (Section III.C) provided a means to screen thousands of mutants. 

Treatment of 3/9,17/S-diacetoxy-5,10-secoandrost-l(10)-en-5-one (164) with BF3. Et20 has been shown to proceed with cleavage of the macrocycle and formation of a new compound (165) containing a cyclopentene ring.140 Based on DFT calculations, a possible mechanism has been proposed involving an intramolecular Lewis acid promoted 2 + 2-cycloaddition, followed by a cycloreversion of the intermediate oxetane (Scheme 45). 

The reactions of alicyclic olefins with Se02 have been extensively investigated. Heating cyclopentene with Se02 in acetic anhydride (acylating oxidation) oxidizes it to much monoacetoxy- and a little diacetoxy-cyclopentene but in a bomb tube at 90-100° much diacetate and little monoacetate are obtained.225 Thus the second methylene group next to the double bond is more or less attacked according to the reaction conditions. 

Enzymatic desymmetrization of cA-l,4-diacetoxy-2-cyclopentene 1260 followed by a series of straightforward functional group manipulations and... 

In order to avoid recrystallization of the optically enriched material (80-86% e.e.), which was obtained from the hydrolysis of weso-l,3-diacetoxy-cyclopentene... 

Papoutsis et al. and Malamidoli-Xenikaki and Spyroudis developed a method to transform 2-hydroxy-1,4-benzo-quinones, such as 132, into 2-cyclopentene-l,4-diones, like 124 112,113 rpjjg pjojocol is based on the thermolysis of a phenyl iodonium, such as 133, ° " which can be prepared treating a hydroxy quinine 132 with the commercially available hypervalent iodine reagent diacetoxy iodobenzene (PhI(OAc)2) (Scheme 18.29). 

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