James R. Vyvyan

Dopamine functions as an antiherbivore defense in the temperate green alga Ulvaria obscura

On northeastern Pacific coasts, Ulvaria obscura is a dominant component of subtidal “green tide” blooms, which can be harmful to marine communities, fisheries, and aquaculture facilities. U. obscura is avoided by herbivores relative to many other locally common macrophytes, which may contribute to its ability to form persistent blooms. We used a bioassay-guided fractionation method to experimentally determine the cause of reduced feeding on Ulvaria by echinoderms, molluscs, and arthropods. Our results indicated that dopamine, which constituted an average of 4.4% of the alga’s dry mass, was responsible for decreased feeding by sea urchins (Strongylocentrotus droebachiensis). Subsequent experiments demonstrated that dopamine also reduced the feeding rates of snails (Littorina sitkana) and isopods (Idotea wosnesenskii). Dopamine is a catecholamine that is a common neurotransmitter in animals. The catecholamines dopamine, epinephrine (adrenaline), and norepinephrine also occur in at least 44 families of higher plants. The functions of catecholamines in plants are less well known than in animals but are likely to be diverse and include both physiological and ecological roles. Our results are the first experimental demonstration of a plant or algal catecholamine functioning as a feeding deterrent. This novel use of dopamine by Ulvaria may contribute to the formation and persistence of harmful Ulvaria blooms in northeastern Pacific coastal waters.

Total synthesis of (±)-heliannuol D, an allelochemical from Helianthus annuus

Abstract The total synthesis of (±)-heliannuol D and its epimer has been completed in 9 steps and 12% overall yield from 2-methylanisole. The benzoxepane moiety of the title compound, a common structural feature in the heliannuol family of natural products, is prepared by a biomimetic opening of an epoxide by a phenol.

Synthesis of the napalilactone and pathylactone A spirocyclic skeleton

The spirolactone core of napalilactone and pathylactone A was synthesized in five steps from 2-methyl-2-cyclohexen-1-one or 2,3-dimethyl-2-cyclohexen-1-one. This spirolactone contains all of the carbon atoms and three of the four stereocenters of napalilactone and pathylactone A.

AN EXPEDIENT TOTAL SYNTHESIS OF ()-CAPARRATRIENE

(±)-Caparratriene has been synthesized by two succinct routes. The first relies on two Wittig reactions and produces (±)-caparratriene and its 2Z isomer as an inseparable 2:1 mixture. The second more efficient synthesis produces only the naturally occurring 2E isomer and proceeds in 36% overall yield. The key step in this short synthesis is the Suzuki coupling of E-2-bromo-2-butene with the E-vinyl borane derived from 4,8-dimethyl-7-nonen-1-yne.

Alkylation of 2-substituted (6-methyl-2-pyridyl)methyllithium species with epoxides

Substituted (6-methyl-2-pyridyl)methyllithium species were reacted with 1,2-epoxyoctane and 2-methyl-2,3-epoxynonane. The monosubstituted epoxide reacted efficiently with lutidyllithium and a number of 2-substituted (6-methyl-2-pyridyl)methyllithium derivatives. The trisubstituted epoxide gave low yields of adducts with all (2-pyridyl)methyllithium species studied. These results are discussed in the context of a proposed synthesis of cananodine.

Efficient Preparation of γ-Hydroxynitriles via Nitrile Enolate-Epoxide Reactions: Scope and Diastereoselectivity

Abstract The nucleophilic opening of epoxides by nitrile enolates using an efficient, convenient protocol is described. The diastereoselectivity of this reaction was explored and found to give syn:anti ratios ranging from 1.1:1.0 to 4.8:1.0. ‡ Camille and Henry Dreyfus Scholar/Fellow 1995–1997.

Synthesis of cananodine by intramolecular epoxide opening

Cananodine is a guaipyridine alkaloid with activity against liver cancer. Cananodine was synthesized using a remarkable intramolecular opening of a trisubstituted epoxide as the key step in construction of the seven-membered carbocycle of the target. The epoxide opening strategy allows all four stereoisomers of cananodine to be prepared.