Alnusonal

From Alnus species i.e. varieties of alder, containing also a large variety of open chain diarylheptanoids (7-21), some biaryl type macrocyclic compounds have also been isolated. In Alnus japonica Steud. indigeneous in Japan Nomura et al. found four diphenols of this kind. The constitution of alnuson (80) and alnusoxide (81) was elucidated in 1975 (20), while alnusdiol (82) and its oxidation product, alnusonol (83) were characterized in 1981 (17). It was observed that 81 could only be isolated from the dried plant and may be therefore an artefact. Alnusdiol was optically active and therefore a trans-diol but its absolute configuration remained unknown. 

Alnusone, a biphenyl-type natural product, was also synthesized by using a dithianyl reagent to open an epoxide ring (Scheme 7). ... 

A more recent version of this type of reaction employs Ni(PPh3)4. Equation 14.58 shows an application to the synthesis of alnusone ... 

Stoichiometric quantities of nickel complexes have been used to achieve the homocoupling of aryl iodides. When the reaction is intramolecular, as in the synthesis of alnuson 2.424 (Scheme 2.134), good yields of unsymmetrical coupling products could be obtained. ... 

Bis(l,5-cyclooctadiene)nickel(0) [Ni(COD)2] reacts with a variety of aryl halides in dirnethylformamide to produce biaryls in good yield. An arylnickel species has been suggested as an intermediate (Semmelhack et al., 1971). By this method 1, -bis(iodoaryl)alkanes are readily converted into the corresponding biphenyl derivatives. The total synthesis of alnusone dimethyl ether (CXLI) shows the usefulness of this procedure (Semmelhack and Ryono, 1975). Tris(triphenylphosphine)nickel is a superior coupling reagent in some instances (Kende et al., 1975). 

Many new and useful biaryl syntheses have been reported during 1981. One of these was nicely used in the first synthesis of the natural product alnusone(6) (Scheme 23). ... 

Example one key cyclization step in an alnusone synthesis involves such a nickel(O) (or palladium (0)) promoted intramolecular coupling of aryl iodide groups [23]. 

Reactions.—, i-Dithianyl Anions. The Corey-Seebach 1,3-dithianyl anion rates as one of the most popular sulphur anions and nucleophilic acylating agents, as demonstrated by its recent use in the syntheses of potential precursors of the macrocyclic antitumour agent maytansine, of cyclopentenones and other unsaturated ketones,of octoses, of lla-hydrox)rprogesterone, of deuteriated aldehydes, of alnusone, of the sex-attractant of the Douglas fir tussock moth, of l,4-diketones, of 3-s-butylglutaraldehyde, of linaloyl... 

---