Spirocyclization strategy toward indole phytoalexins. The first synthesis of (±)-1-methoxyspirobrassinin, (±)-1-methoxyspirobrassinol, and (±)-1-methoxyspirobrassinol methyl ether

The first syntheses of cruciferous indole phytoalexins (±)-1-methoxyspirobrassinin, (±)-1-methoxyspirobrassinol, (±)-1-methoxyspirobrassinol methyl ether as well as a new syntheses of phytoalexins (±)-spirobrassinin and cyclobrassinin were achieved by dioxane dibromide (DDB)-mediated spirocyclization of brassinin and its 1-substituted derivatives.     

Highly stereocontrolled synthesis of [3.3.3] propellane sesquiterpenes. ( ± )-Modhephene and (±)-epimodhephene

Stereospecific total synthesis of (±)-modhephene (2) and (±)-epimodhephene (3) are reported. Conjugate addition of 1-trimethylsilyl-1-butyn-4-yl cuprate (BF₃-etherate catalysis) to bicyclic ketone 6, fluoride ion-promoted deblocking of the terminal acetylene, and ene reaction, gave tricyclic enone 11. Sequential Wittig methylenation, regiocontrolled epoxidation, and Lewis acid catalyzed isomerization afforded ketone 14 whose double bond relocation and Wolff-Kishner reduction led exclusively to 2. In a still shorter route to 3, 3-butenyl cuprate addition to 6 was utilized to gain access to 7. Thermolysis of this intermediate, methylenation, and double bond isomerization were found to deliver pure 3 successfully.     

Synthesis of 28,29-bisnor-(±)-kijanolide

0(26)-Methyl-28,29-bisnor-(±)-kijanolide (23) has been synthesized via aldol reaction of spirotetronate 3 with octahydronaphthalene aldehyde 4 and subsequent macrocyclization of the resulting product.     

Convenient resolution of (±)-piperidine-2-carboxylic acid ((±)-pipecolic acid) by separation of palladium(II) diastereomers containing orthometallated (S)-(−)-1-[1-(dimethylamino)ethyl]naphthalene

(±)-Piperidine-2-carboxylic acid ((±)-pipecolic acid) has been resolved by the fractional crystallisation of diastereomeric palladium(II) complexes containing orthometallated (S)-(−)-1-[1-dimethylamino)ethyl]naphthalene. The enantiomers of the acid were liberated from the individual configurationally homogeneous diastereomers of the complex in high yield with []_D ± 26.0 (c 1.00, H₂O). The crystal and molecular structures of both diastereomers of the complex have been determined.     

First total synthesis of (±)-oxerine

Total synthesis of (±)-oxerine (1), a monoterpene alkaloid, starting from 3-bromopyridine (7) is described. The key reaction in this sequence is the samarium iodide (SmI₂)-mediated intramolecular cyclization of γ-ethynyl bromide (4).     

A stereospecific synthesis of (±)-ferruginol

A stereospecific synthesis of (±)-ferruginol following the Robinson “ring extension” method has been described. The infra-red spectra of the benzoates of the synthetic and natural ferruginol are found to be identical.     

A stereocontrolled total synthesis of (±)-norzizanone

A stereocontrolled total synthesis of (±)-norzizanone 1 has been efficiently accomplished involving base-induced rearrangement of the mesylate 17 as the key step. Aryl participated intramolecular cyclisation of the bromophenol 11 provided the tricyclic dienone 12, which was stereoselectively converted into the mesylate 17.     

A short large scale synthesis of (±) sarkomycin esters

(±) Sarkomycin ethyl ester has been prepared in four steps from ethyl acrylate.     

The total synthesis of (±)-coriolin

The first total synthesis of (±)-coriolin from the tricyclo 6-4-5-fused ring photo-adduct through the key tricyclo 5-5-5-fused ring intermediate, 7,8,11 - trihydroxy - 1,4,4 - trimethyltricyclo[6.3.0.0^2,6]undecan - 3 - one, is described.     

Synthesis of (±)-latifolin dimethyl ether

(±)-Latifolin dimethyl ether has been synthesized by coupling 1,2,4-trimethoxybenzene and o-methoxycinnamyl cation. The isomeric benzylstyrene is also a product of the reaction. Among the possible biogenetic routes for the related compounds present in Dalbergia latifolia the most likely steps seem to be phenylcinnamic esters and 4-phenylcoumarins followed by stages of reduction. The alternative of cinnamyl cation functioning will limit the biosynthesis only to latifolin type of compounds.     

Synthesis of diterpenes—IV Methyl (±)-desisopropyldehydroabietate

The tricyclic ketone (I; R = H) has been synthesized by a new method, and converted into the bromo-ketone (XVII; R = Br). Favorskii rearrangement of the latter gave methyl (±)-desisopropyldehydroabietate (XX).     

Synthese stereoselective DU (±)-β-santalol

We describe here a new convergent and stereoselective synthesis of (±)-β-santalol. This synthesis involves in the last step an original deprotective method of methoxyethoxymethyl ether using pyridinium tosylate.     

A convenient approach to the total synthesis of (±) 4-demethoxydaunomycinone

A convenient and most practical approach to the synthesis of (±) 4-demethoxydaunomycinone starting from 2-methylhydroquinone is described.     

The rearrangement of some cyclopentanone-aryloximes: synthesis of (±)-aplysin, (±)-filiformin and of their debromo analogues.

Upon acid catalyzed rearrangement after Sheradsky, the aryloximes A gave the tricyclic aminals C, which suffered hydrolysis to lactols E. The unique alcohol 29 was then prepared through a highly stereoselective equilibration-reductive alkylation of the epimeric mixture of lactols 22a,b. Two routes, one of which was stereospecific, allowed cyclization of 29 to (±)-aplysin 34. The yield was 2.5 % from oximes 2a,b. The isomeric epi-aplysin 35 and filiformin 36 were also obtained from 29. The debromo analogues 37,38 and 39 and their trideutero derivatives 41,42 and 43 were synthesized along similar line and allowed unequivocal structure elucidation by NMR spectroscopy.     

Synthesis of (±)-halipanicine, a marine sesquiterpene isothiocyanate isolated from an Okinawan marine sponge Halichondria panicea

(±)-Halipanicine, 4-isothiocyanato-1-cadinene, isolated from an Okinawan marine sponge Halichondria panicea was synthesized from (±)-cryptone in 21 steps in 7.7% total yield. The regio- and stereospecific synthesis esablished the relative stereochemistry of halipanicine.     

Total synthesis of (±)-marmin and related coumarin monoterpenes

(±)-Marmin (1a) and its cis isomer (1b) have been synthesized from 7-neranyloxycoumarin (10a) and 7-neryloxycoumarin (10b), respectively, by way of the corresponding terminal epoxides 2a and 2a. The geometrically and positionally specific route confirms the structure and, in particular, the irons double bond geometry of natural (+)-marmin and epoxide (+)-2a. The latter, upon reaction with stannic chloride in benzene gives rise to the naturally occurring cyclic monoterpene coumarin types 3 and 6 as well as the previously unknown double-bond isomer 13.     

Total Synthesis of (±)-Hirsutene via Pd-Promoted Cycloalkenylation Reaction

Beginning with trans-2-methyl-4-cyclohexenecarboxylic acid (9), a total synthesis of linear triquinane sesquiterpene (±)-hirsutene (1) has been accomplished. An acid catalyzed intramolecular conjugate addition (7→6a) and a Pd²⁺-promoted highly stereocontrolled cyclization (5→4) were utilized for the key step of the sequence. Interestingly, some synthetic intermediates exhibited cytotoxicity.     

Synthetic studies on arene-olefin cycloadditions. ii. total synthesis of (±)-isocomene

The arene-olefin meta-photocycloaddition is shown to provide the basis for an effective and general approach to polyquinane natural products as demonstrated by the synthesis of (±)-isocomene (5) in five steps based on Z-2-bromo-2-butene and 2-bromotoluene.     

A synthesis of laudanine and (±)-pseudocodamine: Resolution into the optical isomers

By application of the Bischler-Napieralski reaction, and protection of the phenolic hydroxyl group by benzoylation, laudanine and (±)-pseudocodamine were synthesized. The benzoyl bases were resolved easily with tartaric acid. (+)-Pseudocodamine belongs to the same series as (+)-laudanosine.     

Synthesis of thromboxane A2 analogs—1 : (±)-Dimethanothromboxane A2

The stable thromboxane A₂ analog (±)-dimethanothromboxane A₂ 1 was synthesized from bicyclo[3.1.1]heptane 2 via the tricyclic compound 4.