Microbial oxidation in synthesis: preparation of myo-inositol phosphates and related cyclitol derivatives from benzene

Asymmetric Synthesis of Nabscessin A from Inositol and d-Camphor

An enantiomer of nabscessin A (1), an aminocyclitol amide with antimicrobial activity, was synthesized from myo-inositol and dimethyl d-camphor acetal in 14 steps. Formal synthesis of natural nabscessin A was also achieved through the new approach to access both enantiomers of 4,5-di-O-benzyl-myo-inositol, derived from the same set of starting materials. This synthesis features utilizations of the existing framework of myo-inositol and a regioselective esterification.

The Application of Dioxygenase-Based Chemoenzymatic Processes to the Total Synthesis of Natural Products

This Minireview describes the exploitation of certain enzymatically derived, readily accessible, and enantiomerically pure cis-1,2-dihydrocatechols as starting materials in the chemical synthesis of a range of biologically active natural products, most notably sesquiterpenoids and alkaloids.

Benzoate dioxygenase fromRalstonia eutrophaB9 – unusual regiochemistry of dihydroxylation permits rapid access to novel chirons

Oxidation of benzoic acid by a microorganism expressing benzoate dioxygenase leads to the formation of an unusualipso,orthoarenecis-diol in sufficient quantities to be useful for synthesis.

Design, synthesis, and biological activities of some branched carbasugars: construction of a substituted 6-oxabicyclo[3.2.1]nonane skeleton

Transformation of cyclohexa-2,4-diene-1,2-diylbis(methylene) diacetate to various carbasugars is described. Photooxygenation of a cyclohexadiene derivative gave a bicyclicendoperoxide, which was reduced with thiourea to [2-[(acetyloxy)methyl]cyclohexa-2,4-dien-1-yl]methyl acetate. Epoxidation of the remaining double bond followed by epoxide ring-opening and hydrolysis of the acetate groups gave one of the target hexols. The bicyclic endoperoxide was rearranged to a diepoxide with CoTPP. The diepoxide was reacted with sulfamic acid in acetic anhydride, resulting in the formation of a new branched carbasugar as well as in the formation of cyclitols with a 6-oxabicyclo[3.2.1]nonane skeleton. The mechanism of the formation of the products is discussed. The inhibition activity of six cyclitol derivatives was tested against α-glycosidase.

Discovery of an Escherichia coli esterase with high activity and enantioselectivity toward 1,2-O-isopropylideneglycerol esters

Escherichia coli has been widely used as an expression host for the identification of desired biocatalysts through screening or selection assays. We have previously used E. coli in growth selection and screening assays for identification of Bacillus subtilis lipase variants (located in the periplasm) with improved activity and enantioselectivity toward 1,2-O-isopropylideneglycerol (IPG) esters. In the course of these studies, we discovered that E. coli itself exhibits significant cytoplasmic esterase activity toward IPG esters. In order to identify the enzyme (or enzymes) responsible for this esterase activity, we analyzed eight E. coli knockout strains, in which single esterase genes were deleted, for their ability to hydrolyze IPG butyrate. This approach led to the identification of esterase YbfF as the major E. coli enzyme responsible for the hydrolytic activity toward IPG esters. The gene coding for YbfF was cloned and overexpressed in E. coli, and the corresponding protein was purified and characterized for its biocatalytic performance. YbfF displays a high level of activity toward IPG butyrate and IPG caprylate and prefers the R-enantiomer of these substrates, producing the S-enantiomer of the IPG product with high enantiomeric excess (72 to 94% ee). The enantioselectivity of YbfF for IPG caprylate (E = 40) could be significantly enhanced when using dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) as cosolvents in kinetic resolution experiments. The enzyme also shows high enantioselectivity toward 1-phenylethyl acetate (E ≥ 200), giving the chiral product (R)-1-phenylethanol with >99% ee. The high activity and enantioselectivity of YbfF make it an attractive enzyme for organic synthesis.

Synthesis of 4-C-alkyl inositol 1,4,5-trisphosphates and 1,3,4,5-tetrakisphosphates

The preparation of 2,3,6-O-tribenzyl- and 2,6-O-dibenzyl-myo-inositols with beta-primary, secondary, and tertiary 4-C-alkyl or aryl groups is reported. Five of these novel polyols are elaborated to 4-C-alkyl Ins(1,4,5)P(3) and Ins(1,3,4,5)P(4) analogues. Regio- and stereoselective introduction of 4-C-alkyl or aryl substituents proceeded via a 4-exo-methylene oxide. Subsequent regioselective reduction of an orthobenzoate provided a divergent method to access both InsP(3) and InsP(4) precursors. Previously unreported phosphorylation of the tertiary hydroxyl and global deprotection afforded novel analogues that retain their full complement of polar and charged binding features.

Biology-enabling inositol phosphates, phosphatidylinositol phosphates and derivatives

This review highlights inositol polyphosphate- and phosphatidylinositol-based small molecule probes that have advanced our understanding of intracellular signalling.

Exploratory studies to investigate a linked prebiotic origin of RNA and coded peptides. 3rd communication. Behaviour of 5-amino-1H-imidazole-4-carbonitrile derivatives

The potentially prebiotic synthesis of pyrimidine ribonucleotides by stepwise nucleobase assembly on arabinose-3-phosphate derivatives has been demonstrated in previous work. The generation of xylose-2-phosphate derivatives by aldolisation, and the behaviour of these compounds under the conditions of pyrimidine nucleobase assembly have also been described. In this paper, the scope for generation of purine nucleotides via 3,3'-anhydro-xylo-nucleotides is investigated. In neutral D2O solution, the potential intermediate 47 (Schemes 6 and 8) undergoes H-C2 --> D-C2 exchange, but no appreciable reaction with cyanide or cyanamide occurs. The exchange chemistry expands options for purine nucleobase assembly on sugar phosphate scaffolds.

A novel psychrophilic lipase from Pseudomonas fluorescens with unique property in chiral resolution and biodiesel production via transesterification

A lipase-producing bacterium strain B68 screened from soil samples of China was identified as Pseudomonas fluorescens. With GenomeWalker, the open reading frame of lipase gene lipB68, encoding 476 amino acids, was cloned and expressed in Escherichia coli BL21 (DE3). By affinity chromatography, the recombinant LipB68 protein was purified to the purity of 95%. As a member of lipase subfamily I.3, LipB68 has a unique optimum temperature of 20 degrees C, which was the lowest in this subfamily. In chiral resolution, LipB68 effectively catalyzed the transesterification of both alpha-phenylethanol and alpha-phenylpropanol at 20 degrees C, achieving E values greater than 100 and 60 after 120 h, respectively. Among all the known catalysts in biodiesel production, LipB68 produced biodiesel with a yield of 92% after 12 h, at the lowest temperature of 20 degrees C, and is the first one of the I.3 lipase subfamily reported to be capable of catalyzing the transesterification reaction of biodiesel production. Since lipase-mediated biodiesel production is normally carried out at 35-50 degrees C, the availability of a highly active lipase with a low optimal temperature can provide substantial savings in energy consumption. Thus, this novel psychrophilic lipase (LipB68) may represent a highly competitive energy-saving biocatalyst.

Fluorinated cyclitols as useful biological probes of phosphatidylinositol metabolism

A number of deoxyfluoro cyclitols have been synthesized and evaluated as probes of the phosphatidylinositol pathway (PtdIns pathway), most notably 5-deoxy-5-fluoro-myo-inositol, which is incorporated into the pathway at about 25% the level of myo-inositol itself. Unfortunately, none of the cyclitols have proved effective in limiting cell proliferation, as the cells are able to 'synthesize around' the fraudulent cyclitols using natural myo-inositol as substrate. Inhibitors for 3-phosphatidylinositol kinase, which has importance in a number of pathological conditions, including cancer, have been intensively investigated. 3-Deoxy-3-fluoro-myo-inositol is incorporated into the PtdIns pathway; however, only related phosphatidyl derivatives, for example, a methyl ether derivative of the 3-deoxy inositol, showed significant antiproliferative activity. Synthesis of the deoxyfluoro analogues most often has been accomplished by DAST fluoro-de-hydroxylation of the appropriate cyclitol, generally leading to products of inversion.

[Synthetic studies on sugar-related bioactive substances based on the ring transformation]

The development of two novel ring conversions of sugar derivatives is described. The first is an efficient conversion of 5-enopyranosides and 6-O-acetyl-5-enopyranosides to the corresponding substituted cyclohexanones mediated by a catalytic amount of palladium dichloride. After a survey of various substrates, the reaction was confirmed to be general and useful. Syntheses of bioactive compounds utilizing this method were therefore investigated. Cyclophellitol, which is a potent beta-glucoidase inhibitor, and its diastereoisomer were efficiently synthesized. Furthermore, novel synthesis of all enantiomerically pure diastereoisomers of inositol starting with 6-O-acetyl-5-enopyranosides was investigated. Good accessibility of these enantiomerically pure inositol diastereoisomers results in the efficient syntheses of D-myo-inositol 1,4,5-trisphosphate and D-myo-inositol 1,3,4,5-tetrakisphosphate. The second investigation involved novel and efficient conversion of D-glycono-1,5-lactones into the corresponding L-sugars. The important intermediate, delta-hydroxyalkoxamate, was provided by a practical alkoxyamination of D-glycono-1,5-lactones mediated by Me3Al. In contrast to the preparation of beta-lactam skeletons from beta-hydroxyalkoxamates, the cyclization of delta-hydroxyalkoxamates under Mitsunobu conditions resulted in O-alkylation rather than N-alkylation. It is noteworthy that delta-hydroxyalkoxamates derived from D-mannono-1,5-lactones afforded the O-alkylation product in 91% yield. No N-alkylation product was detected in this case. These O-cyclized oximes, in which the inversion of the configuration at C5 was secured, were efficiently converted into L-sugars.

From 6-t-butylfulvene to highly functionalized five-membered rings

6-t-Butylfulvene was used as the starting material for asymmetric dihydroxylation. The obtained protected diol (2) was used for several stereoselective functionalizations such as epoxidations, hydroboration, and aminohydroxylation. However, these fulvene derivatives proved to be rather unreactive and gave no conversion under, e.g., palladium (0), catalyses or hydroboration conditions.

Enantioselectivity of a recombinant esterase from Pseudomonas fluorescens towards alcohols and carboxylic acids

A recombinant esterase from Pseudomonas fluorescens (PFE) was produced from E. coli cultures and the enantioselectivity towards a series of racemic substrates was investigated. PFE exhibited high rate and enantioselectivity in the acylation of alpha-phenyl ethanol with vinyl acetate in toluene (E > 100) and the hydrolysis of the corresponding acetate in phosphate buffer (E = 58). In sharp contrast, extremely low enantioselectivity (E from 1.1 to 7) was found for the acylation of a series of 1,2-O-protected glycerol derivatives and the hydrolysis of 3-phenylbutyric acid methylester. Almost no reaction occurred with alpha-phenyl propanol and its acetate and 2-phenylbutyric acid ethylester.

A convenient synthesis of D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) and L-myo-inositol 1,4,5-trisphosphate (Ins(3,5,6)P3)

An efficient synthesis of an optically active inositol derivative that is a precursor to D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3, (-)) is described. Crystallization of the diastereomers of (+/-)-1-O-[(+)-menthoxycarbonyl]-6-O-benzyl-2,3:4,5-di-O-isopropyl idene-myo- inositol diastereomers from methanol gives only one diastereomer. Alkaline hydrolysis gives the useful inositol derivative (-)-6-O-benzyl-2,3:4,5-di-O-isopropylidene-myo-inositol. Likewise, crystallization of the diastereomers of (+/-)-3-O-[(-)-menthoxycarbonyl]-4-O-benzyl-1,2:5,6-di-O-isopropyl idene-myo- inositol from methanol gave a pure compound which could be hydrolyzed to give (+)-4-O-benzyl-1,2:5,6-di-O-isopropylidene-myo-inositol, a precursor to D-myo-inositol 3,5,6-trisphosphate (Ins(3,5,6)P3,(+)). The ease with which these enantiomerically pure inositol derivatives were isolated may facilitate the synthesis of more complex inositol phosphate derivatives such as D-myo-inositol 1,3,4,5-tetrakisphosphate.