6334
PETED. GARDNER, RICHARD L. BRANDON AND G. RUFUSHAYNES [CONTRIBUTION FROM THE
DEPARTMENT OF
Vol. 79
CHEMISTRY, THE UNIVERSITY OF TEXAS]
The Structures of p- and y-Lumicolchicine. Ring-D Elaboration Products BY PETED. GARDNER, RICHARD L. BRANDON’ AND G. RUFUSHAYNES~ RECEIVED MAY24, 1957 Evidence is presented which suggests the stereochemical assignment of 1-8 and I-y as the structures of 8- and 7-lumicolchicine, respectively. This assignment is based on a measure of intramolecular hydrogen bonding in each of the corresponding tetrahydro derivatives by studying relative deviations from the Beer-Lambert law. The conversion of 6-lumicolchicine to the y-isomer in basic medium lends support to the hypothesis of a stereomeric relationship between the two. Spectral evidence is presented for the existence of a cyclobutene ring in these substances, and a reduction experiment, from which an amine was obtained, suggests that the acetamido function was not altered in the isomerization of colchicine to I-P and 1-7. Solvolysis studies with the methanesulfonate derivatives of tetrahydro-8- and 7-lumicolchicine led to a series of ring-D elaboration products (X and XII).
Although originally produced artificially, the lumicolchicines have since been isolated from the plant6 and are therefore natural products. A recent paper6 which appeared after our structurestudy with these substances had begun describes evidence leading to the structural assignment of I to the P- and y-isomers, the two being related as diastereoisomers. Since both substances are optically active, i t is reasonable to assume that the configuration about the point of attachment of the acetamido function is the same in the two isomers and identical with that in colchicine. Only a cis fusion of the C-D ring system need be considered and thus, accepting I as the gross structure, I-p and I-y represent the only reasonable structures for these two substances (disregarding for the moment the specific p- and y-assignment). Chemand spectral evidence are consistent with formulation I.
11-7 (tetrahydro-y-lumicolchicine), IIIg, I V 9 and VI are shown with the formulas representing these substances. A comparison of those values for 11-p or 11-7with that for IV (Ah 22 and 26 mp) reveals a large bathochromic shift which corresponds with the auxochromic effect cited above and is en-
111, R =
IV,R
H (259 mp)
= NHAc (254 mp)
CHaO VI (264 mp)
^.-
-HA
