A Highly Effective Diels—Alder Approach to cis‐Clerodane Natural Products: First Total Synthesis of Solidago Alcohol (I).

Ly, Tai Wei; Liao, Jyh-Hsiung; Shia, Kak‐Shan; Liu, Hsing‐Jang

doi:10.1002/chin.200426162

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“…Finally, lactone 81 underwent a four-step synthetic sequence to attain two separable 19-nor-clerodanoid natural products 82 and 83 in racemic form. In addition to the synthetic efforts described above, the utility of -activated cross conjugated cycloalkenone systems was also exemplified in the synthesis of the natural products, including (-)-xenetorin C (84) [35], (±) isoacanthodoral (85) [36], (-)-morphine (86) [37], (-)-qinghaosu IV (87) [38], (±)-solidago alcohol (88) [39], and (±)-montanin A (89) [40] as illustrated in Fig. (5).…”

Section: Synthetic Applications To Formal/total Syntheses Of Natural mentioning

confidence: 99%

α-Activated Cross Conjugated Cycloalkenone Systems in Organic Synthesis

Wu¹,

Ly²,

Shia

2010

COS

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Under catalysis with an appropriate Lewis acid, the intermolecular Diels-Alder cycloaddition and intramolecular polyene cyclization of the -activated cross conjugated cycloalkenone systems, possessing particularly increased dienophilicity/electrophilicity in the cross conjugated double bond, proceeded constantly with a high degree of stereochemical control, leading to a variety of synthetically useful molecules, which may serve as advanced intermediates towards many structurally challenging natural products, especially cisclerodane diterpenoids. Mechanistically, an additional conjugated double bond incorporated into the cycloalkenone core of the titled systems might contribute synergistically to the classical secondary orbital effects, thus significantly enhancing the endo-to-ketone addition. In addition, a tandem multiple -bond migration process, an enzymatic pathway prevalent in nature, was proposed to rationalize the formation of structurally unusual polyene-cyclization products occurring under standard chemical conditions.

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