Methyl levopimarate

OehydroaNetk acid. Methyl dehydroabietaie (2) can be prepared conveniently and in 8S% yield by dehydrogenation of methyl levopimarate (1) with diethyl azodi-carboxylatc in refluxing benzene. ... 

Potassium hydroxide [1, 935-937, before references]. Lawrence et al.10 charged Carius tubes with an ether-methanol solution of methyl levopimarate (1) and 5 mole percent of potassium hydroxide, removed the solvent under reduced pressure, sealed... 

In an aptly titled paper Herz et describe unexpected rearrangements of photolevopimaric acid derivatives. Among a wealth of chemical reactions discussed it appears that the exo-bicyclo[2,2,0]hexanol (575), derived from methyl levopimarate by hydroboration-oxidation, is rearranged during Jones oxidation to the bicyclo[2,l,l]-hexanone (576), contrary to a previous report. A mechanism is proposed. 

The maximum observed rotation for the 2-amino-2-methyl-1-propanol salt of levopimaric acid is [a] n —218°. Methanol and ethanol solutions give the same specific rotations, but methanol is the preferred solvent because the time required to effect solution in ethanol is longer. If pure levopimaric acid, m.p. 151-153°, [a] D —276° is desired, the salt with —210° rotation should be dissolved in 8 parts of boiling methanol, the solution concentrated to the point of incipient crystallization, cooled, and filtered. The yield in this recrystallization is about 70%. 

Amino-2-methyl-l-piopanol in isolation of levopimaric acid, 45, 64 Amino-2-propanone, semicarbazone HYDROCHLORIDE, 46,1 Ammonium chlorophenyldithiocarba-mate, 46, 21... 

The low-temperature ozonolysis of podocarpa-8,1 l,13-trien-12-ol (59) to form the lactol (60) has been re-examined54 and the importance of slightly acidic reaction conditions has been noted. The conversion of podocarpic acid into 19-hydroxypodocarpa-8(14)-en-13-one has been described.55 The C-12 oxygen function was removed by hydrogenolysis of the 12-toluene-p-sulphonate. Details of the nitration of methyl 7-oxodehydroabietate have appeared.56 The conformational analysis of the ring C diene, levopimaric acid, has been discussed57 in terms of a folded conformation. 

Asymmetric induction can be realized with substrates containing one or more stereogenic centers. Levopimaric acid and its methyl ester affords, on treatment with nitrosobenzene in dichloromethane, the corresponding cycloadducts 5 diastereoselectively. The structure of 5 has been determined on the basis of H NMR17. 

The olefin octant rule has been applied to the ti <— n transition of diterpene olefins near 200 nm. The o.r.d. and c.d. curves of levopimaric acid have been interpreted in terms of a folded conformation (4) of ring c which affords relief of the 1,3-diaxial repulsion between the angular methyl group and the 11) -hydrogen atom. 

Chemistry of the Tricyclic Diterpenoids.—The addition of chlorosulphonyl isocyanate to the methyl esters of levopimaric and neoabietic acids with the formation of C-12 carboxyamides has been described.63 The well documented aromatic substitution reactions of dehydroabietic acid continue to be examined,64 together... 

There have been a number of studies of the oxidation of ring c with the object of preparing substrates for the synthesis of more complex diterpenes. The preparation of the keto-acids (75) and (76) from levopimaric acid and of the unsaturated ketone (77) from methyl neoabietate has been described. The ozonolysis of... 

Amino-2-methyl-l-propanol in isolation of levopimaric acid, 46, 64 e-Amino- -nitrobiphenyl, by nitration of o-aminobiphenyl, 46,86 from o,/> -dinitrobiphenyl, 46, 88 AmiNO-2-PIIOPANONE, SEiaCABSAZONE HYDROCSIAtiaOE, 46,1 Ammonia, reaction with 3,4-dichloto-... 

N.m.r. studies on the epimeric 12-hydroxypodocarp-8-enes have shown that ring c exists in a half-chair conformation in which the C-l-C-11 interactions are relieved. O.r.d., n.m.r., and surface-film measurements on levopimaric acid have shown that rings b and c possess a folded conformation. X-Ray analysis has confirmed the conformation (60) in which interactions between the C-10 methyl and the C-11/ hydrogen atom and between the C-1—C-10 bond and the C-1 la hydrogen atom are relieved. 

Methyl jasmonate treatment not only triggers a dramatic change in terpene quantity, but also causes changes in terpene composition. For example, of the two major monoterpenes in the wood, a-pinene and P-pinene, the proportion of a-pinene to P-pinene changed from about 1 1 in control saplings to 1 2 after methyl jasmonate treatment, with increases in the relative amounts of the (-)-enantiomers in relation to the (+)-enantiomers of both compounds. Among the diterpenes, levopimaric acid increased over 5-fold after methyl jasmonate treatment in comparison to a 2.5-fold increase in most of the other major diterpene acids. 

Chernov SV, Shults EE et al (2000) Synthetic transfoimatilevopimaric acid. Russ J Org Chem 36 1623-1633... 

The hydroboration-oxidation and oxymercuration reactions of methyl photo-levopimarate have been investigated. Hydroboration and oxidation gave a mixture of the two alcohols (347) and (348). Oxymercuration of (346) gave the dienol (349). 

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