Eiichi Yoshii

Highly diastereoselective Diels-Alder reaction of optically active ethyl 2-p-tolylsulfinylmethylenepropionate with cyclopentadiene

Abstract Stereochemistry of the Diels-Alder reaction of ethyl Z- and E-2-ptolylsulfinylmethylenepropionate with cyclopentadiene has been studied. The high diastereoselectivity was observed especially in the case of exo-cycloaddition.

Total synthesis of tetronolide, the aglycon of tetrocarcins

Abstract The first total synthesis of tetronolide ( 1 ) has been achieved via coupling of spirotetronate 3 with octahydronaphthalene aldehyde 17 and subsequent macrocyclization of ω-sulfone-α-aldehyde 2 , leading to confirmation of the absolute configuration of 1 .

The first total synthesis of tetronasin (M139603)

Total synthesis tetronasin (1), a tetronic acid polyether ionophore antibiotic, is reported in which the γ-unsubstituted α-acyltetronic acid structure is constructed by cyclization of a β-keto ester derivative 18 derived from tricyclic aldehyde intermediate 17 by reaction with methyl (diazoacetoxy)acetate in the presence of zirconium tetrachloride.

Diels-Alder reaction of α-substituted acrylates and α-(methylene)lactones: Conformation of dienophiles and endo/exo selectivity

Abstract Diels-Alder reaction of 1,6-bis(trimethylsilyloxy)-2,4-hexadiene with α-substituted acrylates and 5 to 7- and 9 to 11-membered α-(methylene)lactones has been carried out to examine correlation of dienophile structure with endo/exo selectivity. While the conformationally flexible acrylates produced cycloadducts of endo/exo = 59:41 to 74:26, the 5 to 7-membered lactones with rigid s-cis conjugate system provide cyloadducts of endo/exo = 13:87 to 32:68 and the 9 to 11-membered lactones which can take both s-cis and s-trans conformation afforded endo/exo ratios of 37:63 to 57:43.

Grignard reaction 0f 2-phenyl-tetrahydropyrrolo-1,5,2-oxazaphospholes, observation of the stereospecific inversion of configuration

Abstract Grignard reaction of bicyclic oxazaphospholes proceeded with inversion of configuration to provide chiral phosphinic esters of known absolute configurations.

Synthesis of (±)-ircinianin, a marine sponge sesterterpene

Abstract A biogenetic-type synthesis of (±)-ircinianin ( 1 ) via intramolecular Diels-Alder reaction of 2 is described.

Pyranonaphthoquinone antibiotics. Part 2. Syntheses of (±)-nanaomycin A and (±)-eleutherins

Two routes for the synthesis of (±)-nanaomycin A (1) starting with 2-bromo-8-methoxy-1,4-naphthoquinone (2) are described. The benzindanone (3) prepared from (2) in three steps was treated with methylmagnesium iodide and then with hydrochloric acid to afford the benzindene (8). Lemieux–Johnson oxidation of (8) gave the ketoaldehyde (9), which was converted into the conjugated ester (10) by reaction with methoxycarbonylmethylenetriphenylphosphorane. Reductive cyclisation of (10) with sodium borohydride afforded a ca. 1 : 1.9 mixture of the cis-naphthopyran (11) and its trans-isomer (12). Oxidative demethylation of (11) and (12) with cerium (IV) followed by treatment with aluminium chloride yielded the corresponding quinones (15) and (16). Ester hydrolysis of (16) formed (±)-nanaomycin A (1). Reductive methylation of the 2-allyl derivative of (2) afforded the bromonaphthalene (18), which was treated with butyl-lithium followed by acetaldehyde to give the naphthylcarbinol (19). The lactol (20) obtained by Lemieux–Johnson oxidation of (19) was treated with trimethyl phosphonoacetate–sodium hydride to yield a ca. 2.1 : 1 mixture of the naphthopyrans (11) and (12). Cyclisation of (19) with mercury-(II) acetate–sodium borohydride yielded a ca. 1 : 0.9 mixture of the cis-naphthopyran (21) and its trans-isomer (22), which were oxidatively demethylated to give (±)-eleutherin (4) and (±)-isoeleutherin (5) respectively.

Methyl α-acyloxy-γ-methylene-β-tetronate. Preparation and use as a building block for the synthesis of the spirotetronic acid structure of chlorothricolide

The Diels-Alder reaction of the title compound 4 and octatrienol 10, which were prepared from 4-methoxy-5-methylene-2(5H)-furanone and furfuryl alcohol or D-glyceraldehyde, respectively, produced in high yield a mixture of stereo- and regio-isomeric spirotetronates: 14, 15, and 16 in about 65:25:10 ratio. The exo-mode adduct 15 (R= 2,4-difluorophenyl) was transformed into carboxylic acid 19, the tetronic acid subunit of chlorothricolide (1), and also to 21 which can be utilized in the synthesis of 1.

An Efficient Synthesis of 3-Cyano-1(3H)-Isobehzofuranones

Abstract Reaction of o-formyl-N, N-diethylbenzamides (5) with trimethylsilyl cyanide affords the corresponding (0-trimethylsi-lyl)cyanohydrins (6), which on treatment with acetic acid produce 3-cyanophthalides (7) in 80–90% isolated yields.

A new synthetic method of 3-acyltetronic acid derivatives and its application to the synthesis of isoaspertetronin a (isogregatin A)

Abstract A new synthetic method of 3-acyltetronic acid derivatives from the corresponding 3-bromo compound via lithiation with n-BuLi followed either by acylation with acid chloride or better by first reacting with aldehyde and then subsequent oxidation with active MnO 2 is described. A revised structure 10 for aspertetronin A(gregatin A) was presented based on the synthesis of the proposed structure 8 and spectral comparison of a model compound 12 with the natural product.