Synthesis of Glycaro‐1,5‐lactams and Tetrahydrotetrazolopyridine‐5‐carboxylates: Inhibitors of β‐D‐Glucuronidase and α‐L‐Iduronidase

The known glucaro‐1,5‐lactam 8 , its diastereoisomers 9 – 11 , and the tetrahydrotetrazolopyridine‐5‐carboxylates 12 – 14 were synthesised as potential inhibitors of β‐D ‐glucuronidases and α‐L ‐iduronidases. The known 2,3‐di‐O‐benzyl‐4,6‐O‐benzylidene‐D ‐galactose ( 16 ) was transformed into the D ‐galactaro‐ and L ‐altraro‐1,5‐lactams 9 and 11 via the galactono‐1,5‐lactam 21 in twelve steps and in an overall yield of 13 and 2%, respectively. A divergent strategy, starting from the known tartaric anhydride 41 , led to the D ‐glucaro‐1,5‐lactam 8 , D ‐galactaro‐1,5‐lactam 9 , L ‐idaro‐1,5‐lactam 10 , and L ‐altraro‐1,5‐lactam 11 in ten steps and in an overall yield of 4–20%. The anhydride 41 was transformed into the L ‐threuronate 46 . Olefination of 46 to the (E)‐ or (Z)‐alkene 47 or 48 followed by reagent‐ or substrate‐controlled dihydroxylation, lactonisation, azidation, reduction, and deprotection led to the lactams 8 – 11 . The tetrazoles 12 – 14 were prepared in an overall yield of 61–81% from the lactams 54, 28 , and 67 , respectively, by treatment with Tf₂O and NaN₃, followed by saponification, esterification, and hydrogenolysis. The lactams 8 – 11 and 40 and the tetrazoles 12 – 14 are medium‐to‐strong inhibitors of β‐D ‐glucuronidase from bovine liver. Only the L ‐ido‐configured lactam 10 (K_i = 94 μM ) and the tetrazole 14 (K_i = 1.3 mM ) inhibit human α‐L ‐iduronidase.     

Synthesis of star‐shaped poly(D,L‐lactic acid‐alt‐glycolic acid)‐b‐poly(L‐lactic acid) with the poly(D,L‐lactic acid‐alt‐glycolic acid) macroinitiator and stannous octoate catalyst

Two types of three‐arm and four‐arm, star‐shaped poly(D,L ‐lactic acid‐alt‐glycolic acid)‐b‐poly(L ‐lactic acid) (D,L ‐PLGA50‐b‐PLLA) were successfully synthesized via the sequential ring‐opening polymerization of D,L ‐3‐methylglycolide (MG) and L ‐lactide (L ‐LA) with a multifunctional initiator, such as trimethylolpropane and pentaerythritol, and stannous octoate (SnOct₂) as a catalyst. Star‐shaped, hydroxy‐terminated poly(D,L ‐lactic acid‐alt‐glycolic acid) (D,L ‐PLGA50) obtained from the polymerization of MG was used as a macroinitiator to initiate the block polymerization of L ‐LA with the SnOct₂ catalyst in bulk at 130 °C. For the polymerization of L ‐LA with the three‐arm, star‐shaped D,L ‐PLGA50 macroinitiator (number‐average molecular weight = 6800) and the SnOct₂ catalyst, the molecular weight of the resulting D,L ‐PLGA50‐b‐PLLA polymer linearly increased from 12,600 to 27,400 with the increasing molar ratio (1:1 to 3:1) of L ‐LA to MG, and the molecular weight distribution was rather narrow (weight‐average molecular weight/number‐average molecular weight = 1.09–1.15). The ¹H NMR spectrum of the D,L ‐PLGA50‐b‐PLLA block copolymer showed that the molecular weight and unit composition of the block copolymer were controlled by the molar ratio of L ‐LA to the macroinitiator. The ¹³C NMR spectrum of the block copolymer clearly showed its diblock structures, that is, D,L ‐PLGA50 as the first block and poly(L ‐lactic acid) as the second block. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 409–415, 2002     

Synthesis of poly(lactide‐ran‐MOHEL) and its biodegradation with proteinase K

Homopoly(L ‐lactide) and homopoly(D,L ‐lactide) were almost inert for biodegradation with tricine buffer or normal enzymes such as bromelain, pronase, and cholesterol esterase but biodegradable with proteinase K. Significantly enhanced biodegradation was observed when an optically active (R)‐ or (S)‐3‐methyl‐4‐oxa‐6‐hexanolide (MOHEL) unit was introduced into poly(L ‐lactide) [poly(L ‐LA)] or poly(D,L ‐lactide) [poly(D,L ‐LA)] sequences. Poly[L ‐LA‐ran‐(R)‐MOHEL] in molar ratios of 86/14 to 43/57 showed good biodegradability that was independent of crystallinity. The biodegradation of polymers with proteinase K increased in the following order: poly[D,L ‐LA‐ran‐(R)‐MOHEL] > poly[L ‐LA‐ran‐(R)‐MOHEL] > poly[D,L ‐LA‐ran‐(S)‐MOHEL] > poly[L ‐LA‐ran‐(S)‐MOHEL] > poly(R)‐MOHEL > poly(D,L ‐LA). The number‐average molecular weight, molecular weight distribution, glass‐transition temperature, and melting temperature did not change before and after the biodegradation of poly[L ‐LA‐ran‐(R)‐MOHEL], indicating that the degradation occurred from the polymer surface. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1374–1381, 2001     

Synthesis of new hydrolyzable polyurethanes from L‐gulonic acid‐derived diols and diisocyanates

New polyurethanes with lactone groups in the pendants and main chains were synthesized by the polyaddition of two kinds of L ‐gulonolactone‐derived diols (2,3‐O‐isopropylidene‐L ‐gulono‐1,4‐lactone and 5,6‐O‐isopropylidene‐L ‐gulono‐1,4‐lactone) with hexamethylene diisocyanate and methyl (S)‐2,6‐diisocyanatohexanoate and by the subsequent deprotection of isopropylidene groups. They were hydrolyzed more quickly than the polyurethane derived from methyl β‐D ‐glucofuranosidurono‐6,3‐lactone in a phosphate buffer solution, the pH value of which was 8.0, at 27 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4158–4166, 2002     

Improved Synthesis of Phytosphingosine and Dihydrosphingosine from 3,4,6‐Tri‐O‐benzyl‐D‐galactal

An efficient and facile synthesis of phytosphingosine and dihydrosphingosine derivatives is described with less steps and in improved overall yield (66–72%) starting from commercially available tri‐O‐benzyl‐D ‐galactal. The key steps include Wittig reaction, Mitsunobu transformation, reduction, and deprotection.     

Syntheses of 2‐Keto‐3‐deoxy‐D‐xylonate and 2‐Keto‐3‐deoxy‐L‐arabinonate as Stereochemical Probes for Demonstrating the Metabolic Promiscuity of Sulfolobus solfataricus Towards D‐Xylose and L‐Arabinose

Practical syntheses of 2‐keto‐3‐deoxy‐D ‐xylonate (D ‐KDX) and 2‐keto‐3‐deoxy‐L ‐arabinonate (L ‐KDA) that rely on reaction of the anion of ethyl 2‐[(tert‐butyldimethylsilyl)oxy]‐2‐(dimethoxy phosphoryl) acetate with enantiopure glyceraldehyde acetonide, followed by global deprotection of the resultant O‐silyl‐enol esters, have been developed. This has enabled us to confirm that a 2‐keto‐3‐deoxy‐D ‐gluconate aldolase from the archaeon Sulfolobus solfataricus demonstrates good activity for catalysis of the retro‐aldol cleavage of both these enantiomers to afford pyruvate and glycolaldehyde. The stereochemical promiscuity of this aldolase towards these enantiomeric aldol substrates confirms that this organism employs a metabolically promiscuous pathway to catabolise the C5‐sugars D ‐xylose and L ‐arabinose.     

A New Route for Preparation of 5‐Deoxy‐5‐(hydroxyphosphinyl)‐ D‐mannopyranose and ‐L‐gulopyranose Derivatives

Starting from methyl 2,3‐O‐isopropylidene‐α‐D ‐mannofuranoside ( 5 ), methyl 6‐O‐benzyl‐2,3‐O‐isopropylidene‐α‐D ‐lyxo‐hexofuranosid‐5‐ulose ( 12 ) was prepared in three steps. The addition reaction of dimethyl phosphonate to 12 , followed by deoxygenation of 5‐OH group, provided the 5‐deoxy‐5‐dimethoxyphosphinyl‐α‐D ‐mannofuranoside derivative 15a and the β‐L ‐gulofuranoside isomer 15b . Reduction of 15a and 15b with sodium dihydrobis(2‐methoxyethoxy)aluminate, followed by the action of HCl and then H₂O₂, afforded the D ‐mannopyranose ( 17 ) and L ‐gulopyranose analog 21 , each having a phosphinyl group in the hemiacetal ring. These were converted to the corresponding 1,2,3,4,6‐penta‐O‐acetyl‐5‐methoxyphosphinyl derivatives 19 and 23 , respectively, structures and conformations (⁴C₁ or ¹C₄, resp.) of which were established by ¹H‐NMR spectroscopy.     

Target‐guided isolation of polar antioxidants from Abelmoschus esculentus (L). Moench by high‐speed counter‐current chromatography method coupled with wavelength switching and extrusion elution mode

An off‐line two‐dimensional high‐speed counter‐current chromatography strategy combined with the wavelength switching technique and extrusion elution mode was successfully developed and applied to the isolation of polar antioxidants from Abelmoschus esculentus (L).Moench. Target‐guided by the result of 2,2‐diphenyl‐1‐picrylhydrazyl screening assay, four antioxidants were obtained with purities over 90% through orthogonal high‐speed counter‐current chromatography separation. UV spectroscopy, mass spectrometry and ¹H NMR spectroscopy were employed to identify their structures, which were assigned as l ‐tryptophan, quercetin‐3‐O‐sophoroside, 5,7,3′,4′‐tetrahydroxyflavonol‐3‐O‐[β‐d ‐rhamnopyranosil‐(1→2)]‐β‐d ‐glucopyranoside, and quercetin‐3‐O‐glucoside. Each monomer exhibited significant antioxidant activity. The results demonstrated that proposed method could be an effective approach to isolate bioactive compounds from complex natural products.     

Structural Characterization and Degradability of Poly(L‐lactic acid)s Incorporating Phenyl‐Substituted α‐Hydroxy Acids as Comonomers

Three types of copolymers of poly(L ‐lactic acid) (PLLA) were synthesized by direct polycondensation of L ‐lactic acid and phenyl‐substituted α‐hydroxy acids (L ‐phenyllactic acid and D ‐ and L ‐mandelic acids). It was found that the glass transition temperature of the copolymers comprising L ‐mandelic acid became significantly higher (from 58 to 69 °C) with increasing content of L ‐mandelic acid (from 0 to 50 mol‐%) although the M _w decreased (from 87 000 to 4 000 Da). The cast films of the L ‐mandelic acid containing copolymers showed improved tensile properties compared with those of the PLLA film. This may be due to a pinning effect of the L ‐mandelic acid units on the helix formation of PLLA, although 30% of the units were racemized. The enzymatic degradability of the L ‐mandelic acid containing copolymers was much higher than that of PLLA, as analyzed with Proteinase K® originating from Tritirachium album.

Synthesis of copolymers of L ‐lactic acid and phenyl‐substituted α‐hydroxy acids.     

L‐arabinitol‐based functional polyurethanes

Three new polymerizable diols, based on mono‐, di‐, and tri‐O‐allyl‐L ‐arabinitol derivatives, were prepared from L ‐arabinitol as versatile materials for the preparation of tailor‐made polyurethanes with varied degrees of functionalization. Their allyl functional groups can take part in thiol‐ene reactions, to obtain greatly diverse materials. This “click” reaction with 2‐mercaptoethanol was firstly studied on the highly hindered sugar precursor 2,3,4‐tri‐O‐allyl‐1,5‐di‐O‐trityl‐L ‐arabinitol, to apply it later to macromolecules. A polyurethane with multiple pendant allyl groups was synthesized by polyaddition reaction of 2,3,4‐tri‐O‐allyl‐L ‐arabinitol with 1,6‐hexamethylene diisocyanate, and then functionalized by thiol‐ene reaction. The coupling reaction took place in every allyl group, as confirmed by standard techniques. The thermal stability of the novel polyurethanes was investigated by thermogravimetric analysis and differential scanning calorimetry (DSC). This strategy provides a simple and versatile platform for the design of new materials whose functionality can be easily modified. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Flavonol Glycosides with α‐Glucosidase Inhibitory Activities and New Flavone C‐Diosides from the Leaves of Machilus konishii

Seventeen flavonoids, five of which are flavone C‐diosides, 1 – 5 , were isolated from the BuOH‐ and AcOEt‐soluble fractions of the leaf extract of Machilus konishii. Among 1 – 5 , apigenin 6‐C‐β‐D ‐xylopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 2 ), apigenin 8‐C‐α‐L ‐arabinopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 4 ), and apigenin 8‐C‐β‐D ‐xylopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 5 ) are new. Both 4 and 5 are present as rotamer pairs. The structures of the new compounds were elucidated on the basis of NMR‐spectroscopic analyses and MS data. In addition, the ¹H‐ and ¹³C‐NMR data of apigenin 6‐C‐α‐L ‐arabinopyranosyl‐2″‐O‐β‐D ‐glucopyranoside ( 3 ) were assigned for the first time. The isolated compounds were assayed against α‐glucosidase (type IV from Bacillus stearothermophilus). Kaempferol 3‐O‐(2‐β‐D ‐apiofuranosyl)‐α‐L ‐rhamnopyranoside ( 12 ) was found to possess the best inhibitory activity with an IC₅₀ value of 29.3 μM .     

Four new ursane‐type saponins from Morina nepalensis var. alba

Four new ursane‐type saponins, monepalosides C–F, together with a known saponin, mazusaponin II, were isolated from Morina nepalensis var. alba Hand.‐Mazz. Their structures were determined to be 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[alpha;‐L ‐rhamnopyranosyl‐(1 → 2)]‐α‐L ‐arabinopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside C, 1 ), 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[alpha;‐L ‐rhamnopyranosyl‐(1 → 2)]‐β‐D ‐xylopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside D, 2 ), 3‐O‐α‐L ‐arabinopyranosyl‐(1 → 3)‐&[beta;‐D ‐glucopyranosy‐(1 → 2)]‐α‐L ‐arabinopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranosyl‐(1 → 6)‐β‐D ‐glucopyranoside (monepaloside E, 3 ) and 3‐O‐β‐D ‐xylopyranosylpomolic acid 28‐O‐β‐D ‐glucopyranoside (monepaloside F, 4 ) on the basis of chemical and spectroscopic evidence. 2D NMR techniques, including ¹H–¹H COSY, HMQC, 2D HMQC‐TOCSY, HMBC and ROESY, and selective excitation experiments, including SELTOCSY and SELNOESY, were utilized in the structure elucidation and complete assignments of ¹H and ¹³C NMR spectra. Copyright © 2002 John Wiley & Sons, Ltd.     

Cancer‐associated pH‐responsive tetracopolymeric micelles composed of poly(ethylene glycol)‐b‐poly(L‐histidine)‐b‐poly(L‐lactic acid)‐b‐poly(ethylene glycol)

To create a novel vector for specifically delivering anticancer therapy to solid tumors, we used diafiltration to synthesize pH‐sensitive polymeric micelles. The micelles, formed from a tetrablock copolymer [poly(ethylene glycol)‐b‐poly(L ‐histidine)‐b‐poly(L ‐lactic acid)‐b‐poly(ethylene glycol)] consisted of a hydrophobic poly(L ‐histidine) (polyHis) and poly(L ‐lactic acid) (PLA) core and a hydrophilic poly(ethylene glycol) (PEG) shell, in which we encapsulated the model anticancer drug doxorubicin (DOX). The robust micelles exhibited a critical micellar concentration (CMC) of 2.1–3.5 µg/ml and an average size of 65–80 nm pH 7.4. Importantly, they showed a pH‐dependent micellar destabilization, due to the concurrent ionization of the polyHis and the rigidity of the PLA in the micellar core. In particular, the molecular weight of PLA block affected the ionization of the micellar core. Depending on the molecular weight of the PLA block, the micelles triggering released DOX at pH 6.8 (i.e. cancer acidic pH) or pH 6.4 (i.e. endosomal pH), making this system a useful tool for specifically treating solid cancers or delivering cytoplasmic cargo in vivo. Copyright © 2008 John Wiley & Sons, Ltd.     

Synthesis and characterization of macroinitiator‐amino terminated PEG and poly(γ‐benzyl‐L‐glutamate)‐PEO‐poly(γ‐benzyl‐L‐glutamate) triblock copolymer

Macroinitiator‐amino terminated poly(ethylene glycol) (PEG) (NH₂‐PEO‐NH₂) was prepared by converting both terminal hydroxyl groups of PEG to more reactive primary amino groups. The synthetic route involved reactions of chloridize, phthalimide and finally hydrazinolysis. Furthermore, poly(γ‐benzyl‐L ‐glutamate)‐poly(ethylene oxide)‐poly(γ‐benzyl‐L ‐glutamate) (PBLG‐PEO‐PBLG) triblock copolymer was synthesized by polymerization of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (Bz‐L‐GluNCA) using NH₂‐PEO‐NH₂ as macroinitiator. The resultant NH₂‐PEO‐NH₂ and triblock copolymer were characterized by FT‐IR, ¹H‐NMR and gel permeation chromatography (GPC) techniques. The results demonstrated that the degree of amination of the NH₂‐PEO‐NH₂ could be up to 1.95. The molecular weight of the PBLG‐PEO‐PBLG triblock copolymer could be adjusted easily by controlling the molar ratio of Bz‐L ‐Glu NCA to the macroinitiator NH₂‐PEO‐NH₂. Copyright © 2004 John Wiley & Sons, Ltd.     

Polyesters analogous to PET and PBT based on O‐benzyl ethers of xylitol and L‐arabinitol

The synthesis, characterization, and some properties of new copolyesters of poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) based on L ‐arabinitol and xylitol are described. These copolyesters were obtained by polycondensation reaction in the melt of mixtures of 1,4‐butanediol or ethylene glycol and 2,3,4‐tri‐O‐benzyl‐L ‐arabinitol or 2,3,4‐tri‐O‐benzyl‐xylitol with dimethyl terephthalate. Their weight‐average molecular weights ranged between 7000 and 55,000, with polydispersities ranging from 1.4 to 4.7. Copolymers containing 1,4‐butanediol could be analyzed by NMR, and were found to have a statistical microstructure. All these copolyesters were thermally stable, with degradation temperatures well above 300 °C. With increasing amounts of alditol in the copolyester, the melting temperature and crystallinity decreased in both series, and the glass transition temperature increased for the PBT series and decreased for the PET series. Only PBT‐derived copolyesters containing a maximum of 10% alditol units showed discrete scattering characteristic of crystalline material. No substantial differences in either structure or properties were observed between the L ‐arabinitol and xylitol copolyester series. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5167–5179, 2008     

Water‐Soluble Polypeptides at Aqueous Interface Produce Extensible Silk‐Like Fiber

A silk‐like extensible poly(α,L ‐amino acid) fiber is created by self‐assembly of poly(α,L ‐lysine) and poly(α,L ‐glutamic acid) at their aqueous solutions' interface. Distinguishing features of the PLL/PLG fiber are the high extensibility and good stretch. Stretching after spinning changes this fiber to a rigid and strong one. The concept and the poly(α,L ‐amino acid) fibers themselves open doors for the production of new protein fibers which are more silk‐ and wool‐like.     

Conformational analysis of the disaccharide methyl α‐d‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d‐mannopyranoside monohydrate

The crystal structure of methyl α‐d ‐mannopyranosyl‐(1→3)‐2‐O‐acetyl‐β‐d ‐mannopyranoside monohydrate, C₁₅H₂₆O₁₂·H₂O, ( II ), has been determined and the structural parameters for its constituent α‐d ‐mannopyranosyl residue compared with those for methyl α‐d ‐mannopyranoside. Mono‐O‐acetylation appears to promote the crystallization of ( II ), inferred from the difficulty in crystallizing methyl α‐d ‐mannopyranosyl‐(1→3)‐β‐d ‐mannopyranoside despite repeated attempts. The conformational properties of the O‐acetyl side chain in ( II ) are similar to those observed in recent studies of peracetylated mannose‐containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C=O bond of the acetyl group. The C2—O2 bond in ( II ) elongates by ～0.02 Å upon O‐acetylation. The phi (?) and psi (ψ) torsion angles that dictate the conformation of the internal O‐glycosidic linkage in ( II ) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated ( II ) using the statistical program MA′AT, with a greater disparity found for ψ (Δ = ～16°) than for ? (Δ = ～6°).     

Separation of α‐amylase inhibitors from Abelmoschus esculentus (L).Moench by on‐line two‐dimensional high‐speed counter‐current chromatography target‐guided by ultrafiltration‐HPLC

In this study, an on‐line two‐dimensional high‐speed counter‐current chromatography system based on a six‐port valve was developed. Target‐guided by ultrafiltration with high‐performance liquid chromatography, the one‐step isolation of three potential α‐amylase inhibitors from Abelmoschus esculentus (L).Moench was achieved by employing the developed orthogonal system and extrusion elution mode. The purities of three potential α‐amylase inhibitors were all over 95% as determined by high‐performance liquid chromatography. Furthermore, UV, mass spectrometry and ¹H NMR spectroscopy were applied to the structural identification of the isolated three target compounds, their structures were assigned as quercetin‐3‐O‐sophoroside (i), 5,7,3′,4′‐tetrahydroxy flavonol‐3‐O‐[β‐d ‐rhamnopyranosil‐(1→2)]‐β‐d ‐glucopyranoside (ii ) and isoquercitrin (iii), respectively. The Results demonstrated that the proposed method was highly efficient to screen and isolate enzyme inhibitors from complex natural products extracts, and on‐line two‐dimensional high‐speed counter‐current chromatography can effectively increase the peak resolution of target compounds.     

Synthesis of poly(D,L‐lactic acid‐alt‐glycolic acid) from D,L‐3‐methylglycolide

D ,L ‐3‐Methylglycolide (MG) was synthesized via two step reactions with a good yield (42%). It was successfully polymerized in bulk with stannous octoate as a catalyst at 110 °C. The effects of the polymerization time and catalyst concentration on the molecular weight and monomer conversion were studied. Poly(D ,L ‐lactic acid‐co‐glycolic acid) (D ,L ‐PLGA50; 50/50 mol/mol) copolymers were successfully synthesized from the homopolymerization of MG with high polymerization rates and high monomer conversions under moderate polymerization conditions. ¹H NMR spectroscopy indicated that the bulk ring‐opening polymerization of MG conformed to the coordination–insertion mechanism. ¹³C NMR spectra of D ,L ‐PLGA50 copolymers obtained under different experimental conditions revealed that the copolymers had alternating structures of lactyl and glycolyl. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4179–4184, 2000     

Electrochemical Determination of L‐Lactate Using Phenylboronic Acid Monolayer‐Modified Electrodes

The surface of a gold (Au) disk electrode was modified with a self‐assembled monomolecular layer of dithiobis(4‐butylamino‐m‐phenylboronic acid) (DTBA‐PBA) to prepare L ‐lactate‐sensitive electrodes. The DTBA‐PBA‐modified electrodes exhibited an attenuated cyclic voltammogram (CV) for the Fe(CN)₆^3? ion in the presence of L ‐lactate, as a result of the formation of phenylboronate ester of L ‐lactate accompanied with the addition of OH^? ion to the boron atom. In other words, the negatively charged DTBA‐PBA monolayer blocked the electrode surface from the access of the Fe(CN)₆^3?/4? ions. Thus, the DTBA‐PBA monolayer‐modified Au electrode can be used for determining L ‐lactate on the basis of the change in redox current of Fe(CN)₆^3?/4? ions. The calibration graph useful for determining 1–30 mM L ‐lactate was obtained.