Constituents of Endiandra species. IV. Isolation of 2-(8'-[(E,E)-5'-phenylpenta-2',4''-dien-1''-yl]bicyclo[4,2,0]octa-2',4'-dien-7'-yl)acetic acid, a biogenetically predicted metabolite of Endiandra introrsa (Lauraceae) and its structure determination by means of 1D and 2D N.M.R. spectroscopy

Abstract

The structure (6a) is proposed for the title compound, on the basis of chemical and spectroscopic data. In particular, a combination of one- and two-dimensional n.m.r. techniques has led to this assignment. Compound (6a) is relatively unstable and its isolation requires a careful extraction process.

Palladium‐Catalyzed Cross‐Coupling Reactions in Total Synthesis

“…As an astounding example of this principle, we highlight here the recent total syntheses by Parker and Lim [105] of SNF4435 C (118) and SNF4435 D (119, Scheme 23), two immunosuppressant agents isolated from a culture broth of Streptomyces spectabilis. [106] The bicyclo[4.2.0]octadiene core structure of these intriguing natural products bears a striking resemblance to that of the endiandric acids, [107] for which a biosynthetic pathway involving an electrocyclization reaction cascade had been proposed by Black and co-workers [108] and subsequently demonstrated experimentally by the Nicolaou group more than 20 years ago. [109] Therefore, by analogy, it was postulated that the SNF compounds arise through sequential conrotatory [ [99][100][101] Scheme 22.…”

“…[97] the said functionality, which, incidentally, highlights once again the sometimes fickle nature of protecting groups in total synthesis. Most recently, Rainier and co-workers have also reported a novel total synthesis of gambierol (108). [101] These researchers made use of the conditions employed by the Yamamoto group to install the unsaturated side chain through a Stille reaction, a transformation that was again left until the very end of the synthetic sequence and which, in this case, proceeded in 75 % yield.…”

Metathesis Reactions in Total Synthesis

“…The viability of this hypothesis was experimentally verified by Parker and Lim who, in the preparation of tetraene 100 through a fragment‐coupling Stille reaction, observed its rapid and spontaneous rearrangement to generate a mixture of 101 and 102 in a ratio closely matching that of the compounds found in Nature 113. Furthermore, related electrocyclization cascades had been proposed as key steps in the biosynthesis of the endiandric acids by Black and co‐workers114 and subsequently demonstrated experimentally by the Nicolaou group115 more than two decades earlier. However, Baldwin and co‐workers noted the striking similarity between tetraene 100 and spectinabilin ( 99 ), the latter being a known natural product isolated from the same producing species ( Streptomyces spectabilis ) more than 25 years earlier by Rinehart and co‐workers 116.…”

Bioinspired Synthesis of (−)‐PF‐1018

“…In the well-known endriandric acid family, for instance, conrotatory 8p electrocyclization of 1 yields cyclooctatriene 2, which then undergoes disrotatory 6p electrocyclization to afford the bicyclo-[4.2.0]octadiene endriandric acid G. This is followed by an intramolecular Diels-Alder reaction that leads to endriandric acid C (Scheme 1 A). [1][2][3] In the case of kingianin A, the electrocyclization cascade yields cyclooctatriene 4 and then bicyclo[4.2.0]octadiene 5, which engages in an intermolecular Diels-Alder dimerization (Scheme 1 B). [4,5] Other examples that have been validated by biomimetic or bioinspired synthesis include ocellapyrone A, [6] where the electrocyclizations are followed by an intramolecular hetero-Diels-Alder reaction, and orinocin, [7] where they are followed by a retro-[2+2] cycloaddition, resulting in "polyene splicing".…”