Enantiospecific synthesis of tricyclo[5.2.1.0]decanes via acid catalysed rearrangement of isotwistanes

An acid catalysed rearrangement was employed for the enantiospecific conversion of isotwistanol to tricyclo[5.2.1.0^4,8]decanes, which provided support for the proposed biosynthesis of allopupukeananes from pupukeananes. The strategy has been further extended to the enantiospecific synthesis of a homobrexane.     

A biogenetically patterned total synthesis of prostaglandin E1

Methyl 11-tert-butyldimethylsilyloxyeicosa-8(Z), 12(E), 14(E)-trienoate was stereoselectively cyclized by treatment with Hg(OCOCF₃)₂ to give a properly functionalized PG skeleton, which was converted to PGE₁ in good over all yield.     

A biogenetically patterned conversion of palmatine into polycarpine

Oxidation of palmatine ($\text{1}$) choride with $\text{m}$-chloroperbenzoic acid in methylene chloride in the presence of sodium bicarbonate at near ?78° C yields polycarpine ($\text{2}$). A new biogenetic route to the aporphines is proposed which does not involve phenolic oxidative coupling, and proceeds through the intermediacy of protoberberinium salts.     

A new total synthesis of the zinc matrixmetalloproteinase inhibitor ageladine A featuring a biogenetically patterned 6pi-2-azatriene electrocyclization

[reaction: see text] A convergent second generation total synthesis of the heterocyclic marine sponge metabolite ageladine A has been achieved by using a biomimetically inspired 6pi-2-azatriene electrocyclization as the key step for formation of the imidazolopyridine moiety.     

A biogenetically patterned synthetic approach to the unusual furan methylenecyclobutanol moiety in providencin

Irradiation of a solution of α,β-unsaturated aldehyde 10 in benzene leads to the methylenecyclobutanol 11 by way of a novel intramolecular C-H insertion reaction. The conversion of 10 into 11 has relevance to the possible origin of the cyclobutane ring-based furanocembrane providencin 1 found in gorgonian octocorals.     

First enantiospecific synthesis of marine nor-sesquiterpene (+)-austrodoral from (−)-sclareol

A short and efficient synthesis of the rearranged nor-sesquiterpenes (+)-austrodoral (1) and (+)-austrodoric acid (2), recently isolated from the Antarctic marine mollusk Austrodoris kerguelenensis, from diterpene (−)-sclareol (4) is reported. The key step of the sequence is the pinacol rearrangement of the drimanetriol 11.     

An enantiospecific synthesis of estrone

Efficient ring cleavage of 9,10-dibromocamphor (3) provides a monocyclic hydroxyacid (5) which can serve as an intermediate in a new enantiospecific synthesis of estrone.     

First enantiospecific synthesis of marine sesquiterpene quinol akaol A

The first enantiospecific synthesis of akaol A, a marine sesquiterpene quinol, has been achieved. Key steps of the synthetic sequence are the oxidative degradation of (-)-sclareol to a dinorlabdane ketoester, mediated by the ozone-lead(IV) acetate system, the diastereoselective α-methylation of a ketoaldehyde, followed by an intramolecular aldol condensation and the further Diels-Alder cycloaddition of a dienol ether.     

An enantiospecific synthesis of a komarovispirane

The enantiospecific total synthesis of a komarovispirane, containing the complete carbon framework, trans-bicyclo[4.3.0]nonanespiro[8.1′]cyclohexane, of the spiroditerpene komarovispirone, starting from the readily available campholenaldehyde is described.     

A high-yielding enantiospecific synthesis of (−)-7-deoxydaunomycinone

A comparison is made between two regiospecific modes of base-catalysed condensation of 4 (or 7)-methoxy-3-phenylsulfonyl phthalides with chiral bicyclic quinone monoketals, one of which occurs in 95% yield and forms the basis of the first enantiospecific total synthesis of (?)-7-deoxydaunomycinone (3).     

Facile enantiospecific synthesis of (+)-iso-cladospolide B

Enantiospecific synthesis of bio-active butenolide (+)-iso-cladospolide B from d-(?)-tartaric acid in a short synthetic sequence is presented. Pivotal reaction sequence includes cross metathesis of an alkene and Wittig olefination.     

Formal enantiospecific synthesis of (+)-FR900482

The enantiospecific synthesis of FK973, and thus a formal enantiospecific synthesis of the antitumor antibiotic (+)-FR900482, is reported. Addition of aniline 8 to chiral epoxide 9, prepared from l-vinylglycine, afforded amino alcohol 12. After protection of the aliphatic nitrogen with the 9-phenylfluoren-9-yl group, to preserve the acidic stereocenter from racemization, formation of the aziridine 14 and intramolecular condensation under basic conditions gave azocinone 15. Hydroxymethylation at the benzylic position was achieved by a process involving methylenation, epoxidation, and hydrogenolysis; the absolute stereochemistry of the resulting alcohol 23 was determined by X-ray crystallographic analysis. The hydroxyl group of 23 was carbamoylated, and the aromatic amine was deprotected electrochemically and then oxidized to give an unstable hydroxylamine that was immediately protected as acetate 26. Oxidation of 26 with DMP, followed by hydrazinolysis of the acetyl group led to spontaneous closure of the resulting N-hydroxyamino ketone to hemiketal 28, which can be considered as a fully protected precursor of FR900482 and derivatives. Acid treatment to remove the protecting groups and acetylation afforded the triacetate FK973.     

First enantiospecific synthesis of (+)-β-herbertenol

The first enantiospecific synthesis of (+)-β-herbertenol, from naturally occurring R-(+)-citronellal, employing Taber's diazo decomposition protocol as the key step, is described.     

An enantiospecific synthesis of (+)-hydroxy-exo-brevicomin

A concise enantiospecific synthesis of the pine beetle pheromone (+)-hydroxy-exo-brevicomin was achieved from l-(+)-tartaric acid in high yield. The key step involves the reduction of a keto-Weinreb amide derived from tartaric acid.     

The first enantiospecific total synthesis of (+)-seychellene

The first enantiospecific total synthesis of the tricyclic sesquiterpene (+)-seychellene, starting from (R)-carvone via (S)-3-methylcarvone, has been accomplished employing a combination of an intermolecular Michael addition-intramolecular Michael addition sequence and an intramolecular alkylation reaction for the generation of the two vicinal quaternary carbon atoms.     

Efficient enantiospecific synthesis of ent-conduramine F-1

An efficient enantiospecific total synthesis of ent-conduramine F-1 (aminocyclohexenetriol) was accomplished starting from the bis-Weinreb amide of tartaric acid. Key reactions in the synthesis include the desymmetrization of tartaric acid amide with vinylmagnesium bromide and installation of the required amine using Ellman sulfinimine. Ring closing metathesis was used to synthesize the required alkene in the cyclohexene.