Flexibilene is a terpene isolated from Sinularia flexibilis, a soft coral found in the Indian Ocean. Draw a stepwise mechanism for the formation of flexibilene from farnesyl diphosphate and isopentenyl diphosphate. What is unusual about the cyclization that forms the 15-membered ring of flexibilene? ... [FREE SOLUTION]

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Chemistry
Organic Chemistry
Chapter 31
Flexibilene is a terpene isolated from Sinularia flexibilis, a soft coral found in the Indian Ocean. Draw a stepwise mechanism for the formation of flexibilene from farnesyl diphosphate and isopentenyl diphosphate. What is unusual about the cyclization that forms the 15-membered ring of flexibilene?

Chapter 31: Flexibilene is a terpene isolated from Sinularia flexibilis, a soft coral found in the Indian Ocean. Draw a stepwise mechanism for the formation of flexibilene from farnesyl diphosphate and isopentenyl diphosphate. What is unusual about the cyclization that forms the 15-membered ring of flexibilene? (page 1257)

Short Answer

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Answer

The unusual feature of cyclization is the generation of a $2^{0}$ carbocation instead of a

$3^{0}$ carbocation.

Step by step solution

Flexibilene

Flexibilene is a diterpene with a chemical formula $C_{20} H_{32}$ , and its structure has a 15-membered ring. It is obtained from farnesyl diphosphate and isopentenyl diphosphate.

Stepwise mechanism of flexibilene

The unusual feature of cyclization is the generation of a $2^{0}$ carbocation instead of a carbocation. The cyclization at the other end of the C=C bond will give a carbocation, and a 14-membered ring will be formed. Moreover, the rearrangement of a $2^{0}$ carbocation into a $3^{0}$ carbocation does not occur.