The rearrangement of a homoallyl cation to a cyclopropylcarbinyl cation is thought to play a role in the biogenesis of a variety of cyclopropane-containing natural products,¹ a hypothesis which has previously led to the design of successful biomimetic syntheses of several natural products.² The strategy underlying this approach to cyclopropane...
Irradiation of a tryptamine linked through its side-chain nitrogen to an alkylidene malonate residue results in an intramolecular [2 + 2] cycloaddition to the indole 2,3-double bond. The resultant cyclobutane undergoes spontaneous retro-Mannich fission to produce a spiro[indoline-3,3-pyrrolenine] with relative configuration defined by the orientation of substituents in the transient...
Studies toward synthesis of subunits of sanglifehrin A, an immunosuppressant featuring a highly substituted [5,5]-spirolactam moiety as well as a 22-membered macrocycle are described. The macrolactone contains a peptidic backbone characterized by an unusual [beta]-substituted (S)-piperazic acid and (S)-m-hydroxyphenylalanine units. These studies resulted in the synthesis of advanced intermediate 358...
An approach to the generation of polyketides was investigated,
which involved ozonolysis of 6, 7 cyclopenteno -1> 4, 5, 8 -tetrahydromethoxy-
3-methylnaphthalene (26), to produce what is believed to be
polyketide 27. Compound 26 was formed by the following sequence:
Die ls -Alder addition of 1, 2 -dim.ethylenecyclopentane and 2...
A synthetic approach toward the two major fragments of cathedulin K-19,
euonyminol (4) and dimethyl cathate (69), was investigated. Synthesis of
dimethyl cathate was accomplished in 3 steps starting from 73. Efforts directed
towards the synthesis of euonyminol, a highly oxygenated dihydroagarofuran
sesquiterpene, was advanced to a stage in which...
Several approaches to the synthesis of methymycin were
investigated. Segment A (39), containing functionality corresponding
to C-9, 10, and 11 of methynolide was made in
six steps from propionaldehyde in an overall yield of 37%.
Oxidation of 34 with silver nitrate gave 35 which, upon hydroxylation
with hydrogen peroxide, gave...