Syntheses and Activities of the Functional Structures of a Glycolipid Essential for Membrane Protein Integration.

MPIase is the first known glycolipid that is essential for membrane protein integration in the inner membrane of E. coli. Since the amount of natural MPIase available for analysis is limited and it contains structural heterogeneity, precisely designed synthetic derivatives are promising tools for further elucidation of its membrane protein integration mechanism.

Asymmetric Ti-crossed Claisen condensation: application to concise asymmetric total synthesis of alternaric acid.

Asymmetric Ti-crossed Claisen condensation utilizing the dioxane-2,5-dione chiral template and its successful application to total synthesis of chiral alternaric acid are described.

MPIase is a glycolipozyme essential for membrane protein integration.

Protein integration into biological membranes is a vital cellular event for all organisms. We previously reported an integration factor in the inner membrane of Escherichia coli, named MPIase (membrane protein integrase). Here we show that in contrast to previously identified integration factors that are proteins, MPIase is a glycolipid composed of diacylglycerol and a glycan chain of three acetylated aminosugars linked through pyrophosphate.

First sequential Mukaiyama-Michael reaction/crossed-Claisen condensation using two molar ketene silyl acetals and one molar alpha,beta-unsaturated esters promoted by a NaOH catalyst.

The NaOH-catalyzed first sequential Mukaiyama-Michael reaction/crossed-Claisen condensation is developed using two molar ketene silyl acetals and one molar alpha,beta-unsaturated esters in either a stepwise or one-pot manner.

Ti-mediated direct and highly stereoselective Mannich reactions between esters and oxime ethers.

The first general method of direct and highly stereoselective Ti-mediated Mannich reaction between three types of simpleesters and E and Z mixtures of oxime ethers (aliphatic and aromatic) is accomplished.

Mild and efficient pentafluorophenylammonium triflate (PFPAT)-catalyzed C-acylations of enol silyl ethers or ketene silyl (Thio)acetals with acid chlorides.

A pentafluorophenylammonium triflate (PFPAT) catalyst (5 mol %) successfully promoted C-acylation of enol silyl ethers with acid chloride to produce various beta-diketones (12 examples; 62-92% yield). Similarly, C-acylation of ketene silyl acetals or ketene silyl thioacetals (i.e.

Highly stereoselective radical carbonylations of gem-dihalocyclopropane derivatives with CO.

A couple of radical carbonylations of gem-dihalocyclopropanes 1 using CO and Bu3SnH (formylation) or Bu3Sn(CH2CH=CH2) (allylacylation) successfully proceeded to give trans and cis adducts (2 and 3) with good to excellent stereoselectivity (trans/cis = >99/1-75/25 or 17/83-1/99). The formylation of 2,3-cis-disubstituted 1,1-dihalocyclopropanes enhanced trans selectivity (trans/cis = >99/1-95/5), whereas both 2,3-cis-disubstituted and 2-monosubstituted 1,1-dihalocyclopropanes underwent allylacylation with nearly complete trans selectivity (trans/cis = >99/1). Inherently less reactive gem-dichloro- and bromochlorocyclopropanes than gem-dibromocyclopropanes served as favorable substrates.

Ti-direct, powerful, stereoselective aldol-type additions of esters and thioesters to carbonyl compounds: application to the synthesis and evaluation of lactone analogs of jasmone perfumes.

An efficient TiCl(4)-Et(3)N or Bu(3)N-promoted aldol-type addition of phenyl and thiophenyl esters or thioaryl esters with aldehydes and ketones was performed (total 46 examples). The present method is advantageous from atom-economical and cost-effective viewpoints; good to excellent yields, moderate to good syn-selectivity, substrate variations, reagent availability, and simple procedures. Utilizing the present reaction as the key step, an efficient short synthesis of three lactone [2(5H)-furanone] analogs of jasmine perfumes was performed.

Insoluble fiber is a major constituent responsible for lowering the post-prandial blood glucose concentration in the pre-germinated brown rice.

The intake of pre-germinated brown rice (PR) instead of white rice (WR) ameliorates the hyperglycemia. To clarify the mechanism(s) to decrease the post-prandial blood glucose concentration, the effect of water-soluble/oil-soluble fraction-depleted PR bran (termed as "DB"; which is destarched and defatted PR bran) on post-prandial blood glucose was compared with that of full-fat PR bran (PB) or WR. The test diets, WR diet, PB diet and DB diet which are containing identical amount of available carbohydrate (1.

Ti-crossed-Claisen condensation between carboxylic esters and acid chlorides or acids: a highly selective and general method for the preparation of various beta-keto esters.

Ti-crossed-Claisen condensation between a 1:1 mixture of carboxylic esters and acid chlorides promoted by TiCl4-Bu3N-N-methylimidazole proceeded successfully to give various beta-keto esters in good yields with excellent selectivities (19 examples, approximately 48-95% yield; cross/self-selectivity = approximately 96/4-99/1). The present method was extended to the condensation between a 1:1 mixture of carboxylic acids and carboxylic esters (six examples, approximately 70-92% yield; cross/self-selectivity = approximately 91/9-99/1). To demonstrate the utility of the present two Ti-crossed-Claisen condensations, we performed a couple of efficient short-step syntheses of two natural, representative, and useful perfumes, cis-jasmone and (R)-muscone.