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A stereoselective formal total synthesis of enigmazole A, a marine macrolide isolated from Cinachyrella enigmatica, is described. Lewis acid mediated intramolecular allylation of an α-acetoxy ether, prepared from alcohol and carboxylic acid fragments was carried out to construct the methylene THP ring with high stereoselectivity. The late-stage macrolactonization of the corresponding seco-acid provided a known synthetic intermediate of enigmazole A.

A convergent total synthesis of (−)-dactylolide is described. Constructing the 2,6-disubstituted exo-methylene THP moiety was achieved by the intramolecular allylation of α-acetoxy ether. The cyclization precursor was prepared from two segments, an alcohol and carboxylic acid derivatives, by esterification followed by reductive acetylation.

With use of the LiTMP-induced Hodgson cyclopropanation of an epoxide-olefin to a bicyclo[3.1.0]hexanol as the key step, a stereoselective total synthesis of photo-mycolactones was achieved. Each of the four diastereomeric epoxide-olefins, selectively prepared from (R)- and (S)-glycidols, yielded the corresponding unique bicyclo[3.1.0]hexanol. Four bicyclo[3.1.0]hexanols 16, dia-16, 19, and dia-19 were converted into four primary alcohols 17, dia-17, 20, and dia-20, the intermediates used in the previous work on photo-mycolactones. This synthesis confirmed the stereochemistry previously proposed for photo-mycolactones.

A new catalytic system (cat. (H)2Phen(Me)2·NiCl2 or (MeO)2Dipyr(H)2·NiCl2, cat. Zr(cp)2Cl2, 2 equiv Mn, and 2 equiv LiCl) has been developed to facilitate the homocoupling of a wide range of aryl, alkenyl, and alkynyl halides.

Total synthesis and structure assignment of the minor metabolite present in lipid extracts of the frog pathogen Mycobacterium liflandii are reported.

Article, TETRAHEDRON LETTERS. 48(26): 4471-4475 (2007)

The title azaazulene 3 was synthesized either by reaction of tropone with N-{(2-pyridyl)acetyl}pyridinium iodide in the presence of ammonium acetate or by palladium-catalyzed cross-coupling between 2-halo-1-azaazulene and 2-substituted pyridine. The compound shows relatively stronger basicity compared with 2,2'-bipyridyl. While 3 showed no emission from the S_1 state but from the S_2 state like azulene does, the diprotonated species of 3, generated in 50％ H_2SO_4 exhibited emission from the S_1 state. Cationic metal-dependent absorption and emission were also studied.

A concise and practical route has been developed for a synthesis of the CH 2 -bridged base pairs represented by the type- II structure. The structural studies suggest the possibility that these base pairs mimic the molecular architecture of Watson–Crick hydrogen-bonded base pairs.

Wacker-type oxidation of cyclopentene to cyclopentanone under dioxygen atmosphere was successfully achieved by the use of Pd(OAc) 2 and molybdovanadophosphate supported on activated carbon, [Pd(OAc) 2 –NPMoV/C], catalyst. Thus, the reaction of cyclopentene under O 2 (1 atm) in aqueous acetonitrile acidified by CH 3 SO 3 H in the presence of [Pd(OAc) 2 –NPMoV/C] at 50°C produced cyclopentanone in 85% yield along with a small amount of cyclopentenone (1%).

The E Z - selectivities in the [2,3]-Wittig rearrangements of secondary β-(methyl or silyl)allylic ethers are shown to depend critically on the nature of groups on the carbanion terminus, thereby permitting elucidation of the structural requirements for attaining high Z-selectivity.

The reaction of keto thioenol ether 6 with dimethylsulfonium methylide gives the isolable epoxide 7 , which smoothly rearranges under thermal conditions to yield the five-membered thioacetal 8 . Subsequent desulfurization/aromatization with a catalytic amount of iodine furnishes the desired furan 5 in greater than 70% overall yield.

The reaction of CeCl 3 •MeLi to tertiary amides has been studied. The reagent prepared from cerium(III) chloride and methyllithium at 0 °C adds cleanly to morpholine amides to give the corresponding methyl ketones. Even in the presence of a large excess of the reagent, no tertiary alcohol formation is observed, indicating that the tetrahedral intermediates are stable under the reaction conditions employed.

Several examples of β-selective C-glycosidation reactions, involving TMSOTf-promoted addition of sterically hindered silyl ketene acetals to glucosyl and galactosyl acetates, are presented.

4-tert-Butylpyridine has been shown to be a beneficial additive in the Ni(II)/Cr(II)-mediated coupling reaction. This additive allows for homogeneous reactions, improves reproducibility, and inhibits homo-coupling of vinyl iodides or triflates. Improved workup procedures using chromium ion chelators (ethylenediamine or sodium or potassium serinate) allow for a better mass recovery . © 1997 Elsevier Science Ltd.

Tolyporphin chromophore 2 has been synthesized by performing a doubleretroaldol/oxidation sequence on an octahydroporphyrin precursor 18 prepared by using the Eschenmoser sulfide-contraction/iminoester-condensation method.

A new method for the synthesis of vinyliodides from vinylsilanes is presented. Using N-iodiosuccinimide in acetonitrile or acetonitrile/monochloroacetonitrile, this transformation is cleanly effected at room temperature under virtually neutral conditions.

Reaction of N-tosylaldimines 1 with methyl isocyanoacetate in the presence of 1 mol % of AuCl(c-HexNC) gave 4-methoxycarbonyl-5-alkyl-2-imidazolines 2 with high (over 89%) cis selectivity. The cis-imidazolinecarboxylates were isomerized into trans isomers by treatment with triethylamine. Hydrolysis of the cis- and trans- imidazolinecarboxylates gave erythro- and threo-α,β-diamino acids, respectively.

The configuration at the chiral centers of the two tricarballylic acid moieties of fumonisin B2 is shown to be R. This stereochemistry is opposite to that recently suggested by others for the tricarballylic acid portions of fumonisin B1 and AAL toxin TA.

The 13 C NMR behaviors of several cyclic and biaryl secondary alcohols as well as acyclic tertiary alcohols have been studied in the chiral bidentate NMR solvent BMBA- p -Me ( 1 ). An empirical rule has been advanced to correlate the absolute configuration of each type of alcohols with the 13 C chemical shift behaviors in ( R , R )- and ( S , S )-BMBA- p -Me.

A concise synthesis of the chromophore proposed for dinoflagellate luciferin was accomplished. The chemical behavior towards molecular oxygen and spectroscopic characteristics of the synthetic chromophore were found to match well with those observed for dinoflagellate luciferin. Comparison of the 13C chemical shifts observed for the E- and Z-isomers of the synthetic model with those observed for dinoflagellate luciferin suggested the natural luciferin to have an E-configuration about its C.15–C.16 olefinic bond.

A stereoselective intramolecular Diels-Alder reaction has been developed using annelated furans to produce functionalized steroidal nuclei, which can serve as advanced intermediates in the synthesis of batrachotoxin.

The oxazepane ring system present in batrachotoxin has been synthesized within the framework of an advanced intermediate via a novel Michael reaction.

The relative and absolute stereochemistry of the backbone of fumonisin B2 is established to be 7a.

NMR chemical shift, 3JHH, 3JCH, nuclear Overhauser enhancement, and optical rotation data suggest that C-sucrose undergoes a conformational change in methanol containing Ca2+, whereas the parent O-sucrose does not.

An efficient, stereoselective synthesis of an enantiomerically pure C-ring precursor 14-S of O-cinnamoyltaxicins-I and -II has been achieved from 3-methyl-2-cyclohexen-1-ol, using a [2,3] Wittig rearrangement as the key step.

A practical, scalable synthesis of the C.1C.13 segment of halichondrin B has been developed starting from L-mannonic-γ-lactone, using C-allylation/oxy-Michael cyclization and Ni(II) Cr(II) -mediated vinyltrimethylsilane addition to set the C.6 C.3 and C.11 stereocenters, respectively.

The tricyclic enone 12, containing the taxane ring system, has been synthesized, using an intramolecular Ni(II)/Cr(II)-mediated coupling of β-iodoenone aldehyde 11 as the key step.

The intramolecular Ni(II)/Cr(II)-mediated coupling reaction of activated olefins with aldehydes is studied in order to identify an ideal arrangement of functionality for construction of the taxane ring system.

Efficient cross-photoaddition of 3-(trans-1-propenyl)coumarin (1a) to olefins occurred to give the corresponding 4 and/or 5-substituted 3-(trans-1-propenyl)-3,6-dihydrocyclobut[c]-2-coumarin (3) in relatively good yields without the formation of dimer of 1a.

The left halves of norhalichondrins and homohalichondrins were synthesized from γ-lactone 1, readily available from D-galactose glycal via Ireland-Claisen rearrangement then iodolactonization.

An efficient synthesis of the C.27–C.38 segment of halichondrins is accomplished, using the Ireland-Claisen rearrangement, Ni(II)/Cr(II)-mediated coupling and Michael reactions as the key steps.

A palladium complex bearing chiral (hydroxyalkyl)ferrocenylphosphine ligand was found to be a highly regio-and stereoselective catalyst for the asymmetric allylic amination of 2-butenyl acetates with benzylamine, the nucleophilic attack of the amine taking place selectively on the more substituted end of the π-allylpalladium intermediate to give optically active 3-benzyamino- 1-butene of up to 84% ee.

A convenient method for the stereoselective construction of angular methyl group of fuzed cyclic ethers is described. Reactions of mixed thioacetals with Me2Zn/Zn(OTf)2 afforded the corresponding methylated products in good yields. Various protective groups such as MOM ether, benzylidene acetal, TBS ether, and pivaloyl group were stable under the reaction conditions.

Novel methods have been developed for the transformation of unsymmetrical 1,3-diketones to β-halo-α,β-unsaturated ketones. These new methods complement known syntheses of this functional group, allowing efficient access to a previously unattainable regioisomer.

Structure of a new cytotoxic squalene-type triterpene, named eurylene, from Eurycoma longifolia was elucidated by spectroscopic data, chemical evidence and X-ray analysis. The absolute stereostructure was determined by an advanced Mosher's method.