Endoperoxides, synthesis

Chiral endoperoxides, synthesis, 260, 261 Chiral hydroperoxides aUyhc alcohol asymmetric epoxidation, 401-6, 407-9... 

Recently, other methods of endoperoxide synthesis have been reported that make the parent 2,3-dioxabicyclo[2.2.1]heptane system, readily available (25, 26, 27). For example, we have been able to prepare from 3-bromocyclopentanehydroperoxide. The trans bromohydroperoxide is converted to in 30 minutes by treatment with silver acetate. The cis bromohydroperoxide reacts much slower and leads to a mixture of products, including... 

Synthesis of Several Analogs of the Prostaglandin Endoperoxide PGH2... 

Synthesis of Prostaglandins via an Endoperoxide Intermediate Stereochemical Divergence of... 

A chemical synthesis of prostaglandins by a free radical pathway through an endoperoxide intermediate showed a strong stereochemical preference for the formation of the endoperoxides having cis alpha and omega appendages. 

Clavulones I and II are members of an unusual family of marine prostanoids from the coral Clavularia viridis which are biosynthesiied by a cationic (i.e. non-radical, non-endoperoxide) pathway. The total synthesis of clavulones I and II was accomplished from cyclopentadiene as SM goal. 

If the double bond could be reduced without severing the peroxide linkage, such endoperoxides. would serve as convenient precursors to the bicyelie peroxides 7. Unfortunately, the synthesis of dihydroascaridole 2a (Eq. 1) is exceptional, for catalytic hydrogenation of endoperoxides generally leads to cleavage of the peroxide bond with formation of the saturated c -l,4-diol. 

The oxidation of 2,5-disubstuted furans by singlet oxygen was exploited for the synthesis of [5,5,5] and [6,5,6] bis-spiroketals <06OL1945>. An unusual regioselective photooxidation of 3-bromofuran to 2- and 3-bromo- hydroxybutenolides, as depicted below, was reported. The mechanism for the observed base-dependent regioselective deprotonation of the endoperoxide intermediate was not determined <06OL4831>. 

Singlet oxygen adds to cyclic 1,3-dienes to afford 1,4-endoperoxides 609). This type of reaction has first been applied successfully to the synthesis of ascaridole from a-terpinene 610) (6.4) and of the vesicatory compound cantharidine 6U) (6.5) some 25 years ago. 

The corresponding endoperoxides of furans usually ring-open to afford 1,4-diketones. Such a sequence, followed by an intramolecular Diels Alder reaction was utilized in the synthesis of the tts-indacenyl dianion (6.7) 613>. 

Endoperoxides of carbocyclic 1,3-dienes are most often transformed into either 1,4-diols, 1,3-diepoxides or 1,4-hydroxyenones. The 1,4-diol formation is illustrated in the synthesis of the sesquiterpene ( )-cybullol (6.8)614). 

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