Chemical and spectroscopic studies lead to the [7,0] metacyclophane structures (2) and (3) for myricanol and myricanone, phenolic extractives from Myrica nagi. X-Ray analysis of the meta-bridged biphenyl, 16-bromomyricanol (nitromethane solvate), by the heavy-atom method, confirmed these assignments, and gave the absolute configuration of myricanol. The compound crystallises in the monoclinic space group P2, with Z = 2 in a unit cell of dimensions a = 6.02 * 0.01. b = 17.34 f 0.02, c = 11 a 2 2 f 0.02 8, and p = 98.4" f 0.2"; the structure was refined to R 0.057 for 1075 independent reflections. C.d. measurements suggest t h a t myricanol prefers t h e same conformation in solution as in the crystalline state. The biphenyl nucleus in 16-bromomyricanot is detormed by metameta-bridging. Similar strain in myricanone (3) is relieved by rearrangement with Lewis acids to the onho,rneta-bridged ketone (1 3). The natural phenols may be biogenetically related to diarylheptanoids.THE stem bark of Mypica nagi (Myricaceae) (reputed to be a fish poison) has been stated 2 to contain the rotenoid (I) among its phenolic constituents, with a t r a n s -~/ c ring fusion of unspecified absolute configuration, and a previously all assigned a C ~S -B / C junction (6aSJ12aS) with ring E attachment, if present,, isoprenoid (or degraded isoprenoid) in character. We have attempted reisolation of the claimed rotenoid, without success. t r 11 10 hexadienyl substituent in ring E. Both reported The phenolic fractions from M . nagi have instead features would be unique among natural rote no id^,^ yielded two unusual meta-bridged biphenyls, myricanol, t Professor Seshadri has informed us that the rotenoid assigne v. K*shnamoodhy, N. R. Krisnaswamy, and T. R. seshadri, ment should now be withdrawn.

The structures of two new lignan constituents of Heliopsis scabra, helianthoidin and helioxanthin. have been determined by spectral and degradative work. The former is shown to be 2-angelyloxy-2-piperonyl-3-veratryl-2S.3S-rbutyrolactone (I), and the latter 1 -(3.4-methylenedioxyphenyl) -2hydroxymethyl-7,8-rnethylenedioxy-3-naphthoic acid lactone (XVII).Heliopsis scabra Dunal. is a North American member of the Compositae, whose roots possess insecticidal activity. The root extractives were examined by Jacobson,l who reported the presence of unsaturated insecticidal isobutylamides, and in addition the presence of two non-toxic crystalline substances was noted. We have re-isolated these crystalline constituents, and now present evidence leading to their formulations as the new lignans (I) and (XVII).?Air dried roots of H . scabra were obtained from the White Mountains of New Mexico.$ From the light petroleum and methylene chloride extracts, two crystalline products were separated by fractional crystallization, or chromatography. One component , helianthoidin, C,&&&[ct]D25 -145.4" (c 162 in CHCl,), formed white needles, m.p. 134-135", and had a weak blue fluorescence in solution. Infrared absorptions at v , , 1770, 1723, and 1648 cm.-l suggested the presence of y-lactone and unsaturated ester functions. In its n.m.r. spectrum helianthoidin displayed signals from two unsaturated methyls (z 7.99, singlet; 7.96, broad doublet), and an olefinic proton ( T 3.65-3.84, broad). On hydrogenation over palladium catalyst the compound gave a dihydro-derivative, CsH3,08, m.p. 83-85", with vmxs 1770 (y-lactone) and 1738 (saturated ester) cm.-l, and the n.m.r. spectrum of this now showed two saturated methyls ( 7 9.00, triplet; 8.75, doublet) to be present. Ozonolysis of helianthoidin afforded acetaldehyde (2,4-dinitrophenylhydrazone).These data suggested that helianthoidin might be an ester of either tiglic or angelic acid. This was Confirmed by pyrolysis. Helianthoidin decomposed smoothly on heating, yielding as the volatile product, a mixture of angelic and tiglic acids in which the former predominated. The acids were identified by g.1.c. comparison of their methyl esters with authentic specimens. Since helianthoidin is a pure crystalline substance, it must be the angelate ester, some cis _+ trans isomerization having taken place during pyrolysis. In agreement with this conclusion, the broad olefinic proton in helianthoidin appears at 3-75 (centre) ; the corresponding protons in angelic and tiglic acids are found at 3-83 and 3.03 respectively. The residue from this pyrolysis experiment contained a new lactone, m.p. 129-130°, [ct]D26 -83.3" (c 0.56 in CHCI,), with A , , 232-5 (4.22), 287 (4.02), 295 (4.01), and 332 (4.21) mp, v , ,

No abstract

No abstract

The proton magnetic resonance spectra of natural rotenoids and their relatives have been explored. Much structural information is quickly accessible by this means and the asymmetric shielding of the 1-proton by the 12-carbonyl group can be used to decide the cis-or trans-fusion of the B/C rings. Comment is made on the structure of neotenone, a new isoflavanoid.OWING' to the difficulties in the isolation of rotenone-like compounds from natural sources, small quantities only are sometimes available and considerable use must be made of physical methods for structural analysis. In this paper, the application of high-resolution proton magnetic resonance spectroscopy to the problem is examined and it is shown that immediate insight into many details of structure is gained. Our main quantitative results are in the annexed Table. the expected negative shieldings [cf. 12-deoxy-6',7'-dihydrorotenone (IVb ; R = H) (T 3-34)]. Rotenolone B' (IIIa; R = OH, R = H) and isorotenolone B (IIIc; R = OH, R' = H), and their methyl ethers: have T values of about 2.0 for their l-hydrogen atoms and this is consistent with the rigid and fairly flat trans-B/c fusion (VI; R = OH or OMe), ' Jackman, " Applications of Nuclear Magnetic Resonance Spectroscopy in Organic Chemistry, "

No abstract

cis-and (f )-trans-Chrysanthemic acid yield the expected homochrysanthemic acids on Amdt-Eistert homologation : in the ( f )-cis-case rearrangement to a cyclobutane, as has been alleged, does not occur. Oxidation of these acids gives (*)-cis-and ( f )-trans-homocaronic acid. Widmark's views on Simonsen's results are confirmed. Earlier specimens of the alleged cis-acid were 3,3-dimethylbutene-1 ,.l-dicarboxylic acid and the only previous authentic material is the (+)-acid obtained by Widmark's degradation of the (+)-car-3-ene. By synthesis linking them to the chrysanthemic acids, the absolute configurations of (+)and (-)-cis-and (+ )and (-)-trans-homocaronic and homochrysanthemic acid are worked out. This also links the assignments for the chrysanthemic acids with that separately arrived a t for (+)-car-3-ene and agreement is found.The absolute configuration of the chrysanthemic acids previously rested on isolating C-2 as pyrocin and degrading the latter [in the case of the natural (+)-trans-acid] to (+)-terebic acid. ( +)-trans-Homochrysanthemic acid is now converted into a lactone in which C-1 of the parent (+)-transchrysanthemic acid is isolated and recovered, this time as (-)-terebic acid.Alkaline fission of the homocaronic esters, which is not complete and does not occur with the free acids, is discussed: it is encountered in ethyl 2-ethoxycarbonykyclopropylacetate and a case of vinylogous fission is mentioned. I n an addendum, the earlier assignment of trans-side-chain configuration to natural chrysanthemum dicarboxylic acid from the pyrethrins is confirmed by nuclear magnetic resonance measurements.

No abstract