Jun-ichi Sakaki

Derivatives of α,α,α',α'-tetraaryl-2,2-dimethyl-1,3-dioxolan-4,5-dimethanol (TADDOL) containing nitrogen, sulfur, and phosphorus atoms. New ligands and auxiliaries for enantioselective reactions

Abstract α,α,α′,α′-Tetraaryl-2,2-dimethyl-1,3-dioxolan-4,5-dimethanols are converted to bicyclic phosphites and phosphonites (2a–2e) by reaction with Cl2PR and Cl2POR derivatives. - One or both OH groups of the parent TADDOL can be replaced by Cl (→, 4a, 5a), and the halide in turn substituted by azide (→ 4b, 5b), thiocyanide (→ 6), or sulfide (→ 8). Reduction of the azido group(s) to NH2 and N-alkylation or acylation furnishes a variety of amino alcohols (4c–4f) and diamines (5c–5f), as well as a bis(trifluoroacetamide) (5g). Cyclization of the aminoalcohol (4c) produces a bicyclic system (7), containing a pyrrolidine ring (structure determination by X-ray diffraction). - The new chiral compounds containing nitrogen and phosphorus atoms might be useful ligands and auxiliaries for enantioselective syntheses.

Two lactone formation reactions from 1,3-dioxin-4-ones having hydroxyalkyl group at the 6-position: Difference in ring opening and closure☆

Abstract Two methods (A: ring opening to acylketenes followed by intramolecular ketene trapping and B: methoxide-mediated ring opening followed by cyclization of the hydroxy esters thus formed) have become available for the synthesis of lactones and/or cyclic ethers from 1,3-dioxin-4-ones having 1-∼ 4-hydroxyalkyl group at the 6-position. Mechanism and scope of both methods have been clarified.

Lipase-catalyzed asymmetric synthesis of 6-(3-chloro-2-hydroxypropyl)-1,3-dioxin-4-ones and their conversion to chiral 5,6-epoxyhexanoates

Abstract Highly enantioselective syntheses of ( R )- and ( S )-6-(3-chloro-2-hydroxypropyl)-1,3-dioxin-4-ones by means of lipase-catalyzed kinetic resolutions are described. Chiral dioxinones thus obtained have been converted to optically active 5,6-epoxyhexanoates, which are important precursors for a series of biologically active compounds.

1,3-Dipolar cycloaddition of di-1-menthyl benzylidenemalonate to (z)n,α-diphenylnitrone: Explanation for diastereoselectivity

Abstract 1,3-Dipolar cycloaddition of di-1-menthyl benzylidenemalonate to (Z)-N,α-diphenylnitrone proceeds by Si-face preference to give the endo-adduct as the major product among all four possible adducts. An explanation for this diastereofacial selectivity (Si-face preference) is proposed based on X-ray crystallographic analysis of the malonate as well as effects of high-pressure to the ratio of the adducts.

Synthesis of 1,3-dioxin-4-ones having chiral hydroxyalkyl groups at the 6-position by means of baker's yeast reduction and their uses for epc synthesis

Abstract Prochiral methyl ketones connected with 6-(4-oxo-1,3-dioxinyl) group directly or through methylene chain (1–3) gave, by treatment with fermenting bakers yeast, the corresponding ( S )-alcohols which served as synthons for a variety of enantiomerically pure compounds.

Highly enantioselective reduction of acetoacetylated meldrum's acid with fermenting baker's yeast

Abstract Acetoacetylated Meldrums acid was enantioselectiviely reduced with fermenting bakers yeast to afford the corresponding chiral (S)-alcohol, which could be easily converted to δ-lactone derivatives.

Use of 1,3-dioxin-4-ones and related compounds in synthesis. Part 39. Enantioselective synthesis of 1,3-dioxin-4-ones having 2,3-dihydroxy- or 2,3,4-trihydroxyalkyl groups at the 6-position: versatile building blocks of polyhydroxylated 4–7 carbon backbones

1,3-Dioxin-4-ones having 3-hydroxyprop-1-enyl and 2-hydroxybut-3-enyl groups at the 6-position afford, after the Sharpless asymmetric epoxidation followed by epoxide ring cleavage, the 6-[(2S)-2,3-dihydroxypropyl]- and 6-[(2S,3R)-2,3,4-trihydroxybutyl)dioxinones. The former acts as a four-and six-carbon building block, while the latter as a five- and seven-carbon building block.

Studies on amino acid derivatives. Part 7. General method for the synthesis of penam and cepham and their substituted derivatives

Penam (7-oxo-4-thia-1-azabicyclo[3.2.0]heptane), a basic skeleton of penicillin-type β-lactams, has been synthesized as a stable compound from thiazolidinylacetic acid. The key step in this synthesis is the formation of the β-lactam ring by Mukaiyama-Ohnos procedure. Three methods are developed for the synthesis of thiazolidinylacetic acid from cysteamine by reactions with ethyl propiolate, ethyl ethoxycarbonylacetimidate, or t-butyl formylacetate. Using appropriate derivatives of the latter compounds, 5-, 6-, and 5,6-substituted derivatives of penam are also synthesized. The yields of the bicyclic β-lactams are shown to be strongly dependent upon the pattern of substituents on the thiazolidinylacetic acid. The synthesis of cephams using homocysteamine is also described.

(6S, 7S, 10R)- and (6R, 7S, 10R)-7-isopropyl-10-methyl-4-oxo-1,5-dioxaspiro[5.5]undec-2-enes having an electron-withdrawing substituent at the 2-position: synthesis and use in asymmetric Diels–Alder reactions

Chiral spirocyclic dioxinones (S)-(6) and (S)-(7) have been synthesized from (–)-menthone and used in Diels–Alder reactions with cyclopentadiene; remarkable diastereofacial selectivity (isopropyl side) and endo preference observed in these reactions have offered a new methodology for asymmetric Diels–Alder reactions.

Enantioselective synthesis of (S)- and (R)-6-(2,3-dihydroxypropyl)-1,3-dioxin-4-ones: the versatile building blocks of four- and six-carbon backbones

The Sharpless asymmetric epoxidation of 2,2-dimethyl-6-(3-hydroxy-1-propenyl)-1,3-dioxin-4-one using titanium tetraisopropoxide–diisopropyl tartrate followed by catalytic hydrogenation affords the title compounds as enantiomerically pure compounds, which act as versatile four- and six-carbon building blocks.