Oxabicyclo heptene derivatives

An example of the Diels Alder reaction of furans is the cycloaddition of 31 with 4,4-diethoxybut-2-ynal (32) which acts as an acetylenedicarbaldehyde synthon to afford 7-oxabicyclo [2.2.1]heptene derivatives [29] which were then converted into substituted cyclohex-l-ene-l,6-dicarbaldehydes by a four-step procedure (Scheme 2.14). 

The 7-azabicyclo[2.2.1]heptene derivative (57) decomposes in hot aqueous sodium carbonate solution to give A-benzylpyrrole-3,4-dicarboxylic acid and, presumably, ethylene. Furan-3,4-dicarboxylic acid derivatives are formed analogously on heating the 7-oxabicyclo-[2.2.1]heptene diesters (58). The only thermal decomposition of a... 

Chiral Auxiliary for Cycloaddition Reactions. Cam-phanate ester (11) has been used as a chiral dienophile in cycloaddition reactions with substituted furans to produce 7-oxabicyclo[2.2.1]heptene derivatives (eq ). ... 

CAB 3c derived from N-tosyl (a5 / )-/3-methyltryptophan catalyzes the Diels-Alder reaction of 2-bromoacrolein and furan with 96 4 enantioselectivity, enabling efficient synthesis of numerous chiral 7-oxabicyclo[2.2.1]heptene derivatives (Eq. 17) [18]. Interestingly, the analog 3b of catalyst 3c which lacks the y8-methyl group (derived from M-tosyl-(5)-tryptophan) is not as effective at catalyzing the formation of Diels-Alder product, and the reaction rate and yield are considerably lower. 

Oxabicyclo[2.2.1]heptene derivatives 21a and 2lb are conveniently prepared via the Diels-Alder reaction of cyanovinyl acetate with furan (see Section 1.6.1.1.1.2.2.2). These compounds add to cyclopentadiene (2) with very high exo selectivity. [4 + 2] Cycloaddition of cyclopenta-diene to 21a proceeds easily to afford a mixture of 22a and 23a with a d.r. (anti/syn) 93 7. Similarly, addition to 21b produces a mixture of 22b and 23b with a d.r. (anti/syn) 90 1023. 

Butz and Sauer investigated the intramolecular Diels-Alder reaction of furfuryl fumarates 148 to synthesize oxabicyclo[2.2.1]heptene derivatives 149 and 150 (Scheme 8.37) [69]. Four new stereocenters of defined configuration are generated in this transformation under the induction of the stereogenic center in the side arm with remarkable selectivity. The cycloaddition of 148 with various substituents R at the stereogenic center was investigated and it was found that the diastereo-... 

Diels-Alder reactions of furan provide a straightforward access to the 7-oxabicyclo[2.2.1]heptane skeleton, which is a constituent of many biologically relevant and natural products such as solanoeclepin A [5], glycinoeclepin A [6], and cantharidin. In addition, 7-oxabicyclo[2.2.1]heptene derivatives have been shown to be valuable key intermediates for the S5mthesis of important types of natural products [7], A large number of selective transformations of the 7-oxabicyclo[2.2.1]heptene system endow this nucleus with impressive versatility. 

Additional noncoagulating thromboxane agonist derivatives were prepared by the authors (1) in an earlier investigation. [15 -[la,2a-(Z),3P-(l , 3S, ) ta]]-7-[3-(3-hydroxy)-4-(4-iodophenoxy)-1 -butenyl]-7-oxabicyclo[2.2. l]hept-2-yl]-5-hepten-l -ol, (II), is especially preferred for treating acute angle-closure glaucoma. 

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