Simultaneous determination of six perylenequinones in Shiraia sp. Slf14 by HPLC

The aim of the study was to develop a rapid and sensitive analytical method for simultaneous determination of the hypocrellin A, hypocrellin B, hypocrellin C, elsinochrome A, elsinochrome B, and elsinochrome C content in the Huperzia serrata endophytic fungus Shiraia sp. Slf14. Separation was performed by high-performance liquid chromatography (HPLC) with an YMC-Triart C18 column (4.6?mm?×?250?mm, 5?µm), elution with acetonitrile and triple-distilled water (volume ratio 70:30) as the mobile phase, a detection wavelength of 460?nm, and a flow rate of 1.0?mL/min. All six pigments were successfully determined with good linear correlations and a precision relative standard deviation <2.3%. The methodology was applied to simultaneously measure the concentration of perylenequinones and their derivatives during submerged fermentation and proved adequate for analysis of the biosynthesis of perylenequinones.     

北醌类光敏色素的生物催化合成

北醌化合物是一类具有光敏活性的色素 .近年来 ,发现它们具有良好的光敏杀伤肿瘤细胞[1] 和抑制爱滋病病毒 HIV- 1的作用 [2 ] ,曾用于治疗皮肤病和皮肤癌[3 ] .而且北醌化合物还是潜在的新型光电转换材料 [4 ] .赵晨等人合成了这类具有独特立体结构的真菌次生代谢产物的北醌衍生物 ,并将其用作竹红菌素的前体 [5,6] .Broka[7]采用十几步反应合成了 3种北醌化合物 .生物合成作为 2 1世纪的新兴学科 ,正在迅速发展 .利用生物合成目标分子化合物 ,以专一性、低成本见长 .由于现有竹红菌资源有限 ,化学合成成本太高 ,严重地制约了这类药物的…     

Transition metal-boron complexes BnM: from bowls (n = 8-14) to tires (n = 14)

Transition metal-boron complexes BnM have been predicted at density functional theory level to be molecular bowls (n = 8-14) hosting a transition metal atom (M) inside or molecular tires (n = 14) centered with a transition metal atom. Small Bn clusters prove to be effective inorganic ligands to all the VB-VIIIB transition metal elements in the periodic table. Density functional evidences obtained in this work strongly suggest that bowl-shaped fullerene analogues of Bn units exist in small BnM complexes and the bowl-to-tire structural transition occur to the first-row transition metal complexes BnM (M = Mn, Fe, Co) at n = 14, a size obviously smaller than n = 20 where the 2D-3D structural transition occurs to bare Bn. The half-sandwich-type B12Cr (C3v), full sandwich-type (B12)2Cr (D3d), bowl-shaped B14Fe (C2), and tire-shaped B14Fe (D7d) and B14Fe- (C7v) are the most interesting prototypes to be targeted in future experiments. These BnM complexes may serve as building blocks to form extended boron-rich BnMm tubes or cages (m > or = 2) or as structural units to be placed inside carbon nanotubes with suitable diameters.     

Temperature dependence of the crystal lattice organization of coordination compounds involving nitronyl nitroxide radicals: a magnetic and structural investigation

Four new mononuclear complexes of formula Cd(PN)(4)(NCS)(2) (A), Cd(PNN)(4)(N(3))(2) (B), Zn(PNN)(4)(N(3))(2) (C), and Zn(PNN)(2)(NCS)(2) (D), where PNN stands for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and PN for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl, were synthesized and structurally and magnetically characterized. The X-ray structures of compounds B and C were also determined at 90 K. Compounds A[bond]C crystallize in the triclinic space group P 1 macro (No. 2), and D crystallizes in the monoclinic space group P2(1)/m (No. 11). A[bond]C adopt a centrosymmetric distorted octahedral geometry in which the metal ions are bonded to four radical ligands through the nitrogen atom of the pyridyl rings and the azido or thiocyanato ligands occupy the apical positions. Compound D adopts a distorted tetrahedral geometry in which the zinc ion is bonded to two radicals and two thiocyanato ligands. As suggested by their magnetic behavior, the low-temperature X-ray structures of B and C show that these compounds undergo a clear structural change with respect to the room-temperature structures. The experimental magnetic behaviors were perfectly reproduced by a dimer model for A[bond]C and an alternating chain model for D while the sudden breaks observed in the chi(M)T versus T curves for B and C were well accounted for by the high- and low-temperature X-ray structures. For all these complexes the crystal structures favor significant overlap between molecular magnetic orbitals leading to rather strong intermolecular antiferromagnetic interactions.     

Total synthesis of piericidin A1 and B1 and key analogues

Full details of the total synthesis of piericidin A1 and B1 and its extension to the preparation of a series of key analogues are described including ent-piericidin A1 (ent-1), 4'-deshydroxypiericidin A1 (58), 5'-desmethylpiericidin A1 (73), 4'-deshydroxy-5'-desmethylpiericidin A1 (75), and the corresponding analogues 51, 59, 76, and 77 bearing a simplified farnesyl side chain. The evaluation of these key analogues, along with those derived from their further functionalizations, permitted a scan of the key structural features providing new insights into the role of the substituents found in both the pyridyl core as well as the side chain. A strategic late stage heterobenzylic Stille cross-coupling reaction of the pyridyl core with the fully elaborated side chain permitted ready access to the analogues in which each half of the molecule could be systematically and divergently modified. The pyridyl cores were assembled enlisting inverse electron demand Diels-Alder reactions of N-sulfonyl-1-azabutadienes, while key elements of side chain syntheses include an anti selective asymmetric aldol to install the C9 and C10 relative and absolute stereochemistry (for natural and ent-1) and a modified Julia olefination for formation of the C5-C6 trans double bond with convergent assemblage of the side chains.     

Do penta- and decaphospha analogues of lithocene anion and beryllocene exist? Analysis of stability,structure, and bonding by hybrid density functional study

Stability in penta- and decaphospha analogues of lithocene anion and beryllocene is investigated by complete structural optimization at the B3LYP/6-31G level. Natural bond orbital analysis is carried out to examine the bonding between the metal and the ligands. The heterolytic dissociation energies of 667 and 608 kcal/mol predicted by B3LYP/6-311+G//B3LYP/6-31G calculations for CpBeP(5) and (P(5))(2)Be are comparable with the observed value of 635 +/- 15 kcal/mol in ferrocene. The high stability in CpBeP(5) and (P(5))(2)Be shows that these species are isolable under appropriate conditions. Lithocene anion and its phospha analogues possess lower stability toward dissociation into ionic fragments. A novel observation of the present study is that CpBeP(5) and (P(5))(2)Be have lowest energies when the two planar ligands are arranged perpendicular to each other such that one of the ligands, cyclo-P(5), is eta(1)-coordinated while the second ligand is eta(5)-coordinated to Be. The resulting structure having C(s)() point group (denoted as C(s)()(p)) is predicted to be 22 and 28 kcal/mol lower than the staggered sandwich geometry in CpBeP(5) and (P(5))(2)Be, respectively, at the B3LYP/6-311+G//B3LYP/6-31G level. In the analogous lithocene anions [CpLiP(5)](-) and [(P(5))(2)Li](-) also the C(s)()(p) structures are found to be the lowest energy structures, though their relative stabilities are small. We also characterized the geometry with both ligands eta(1)-coordinated to the metal in a linear arrangement having the D(2)(h)() point group in the decaphospha analogues [(P(5))(2)Li](-) and (P(5))(2)Be. This structure is found to be higher in energy than the C(s)()(p) structure. The D(2)(h)() structure could not be located as a potential minimum in the biscyclopentadienyl complexes and their pentaphospha analogues. Both the C(s)()(p) and D(2)(h)() structures are characterized for the first time in metallocenes. The D(2)(h)() structure seems to be a unique feature in the decaphospha metallocenes under consideration. Covalent bond formation between beryllium and phosphorus atom P(1) of eta(1)-(cyclo-P(5)) is more pronounced (bond orders 0.43-0.49) than that between Be and C(1) of eta(1)-Cp (bond orders 0.24-0.27). Though both eta(1)-coordinated cyclo-P(5) and Cp exhibit C(2)(v)() point groups, bond alternation is less pronounced in the former. The Wiberg P-P bond orders in the eta(1)-(cyclo-P(5)) of CpBeP(5) and (P(5))(2)Be having C(s)()(p) structures are in the range 1.29-1.47. These ring bond orders indicate that the P(5) ring retains aromaticity to a large extent in the eta(1)-mode of bonding with Be. Second-order perturbational energy analysis of the Fock matrix in the natural bond orbital basis reveals that there is a significant stabilizing interaction of approximately 123 kcal/mol between the lone pair orbital of P(1) and the 2s orbital of Be in the C(s)()(p) structures.     

Total synthesis of (±) aspidostomide B,C, regioisomeric N-methyl aspidostomide D and their derivatives

A full account of the total synthesis of aspidostomide B, C, their analogues and our synthetic efforts towards the synthesis of aspidostomide D, which led to the synthesis of regioisomeric N-methyl aspidostomide D, its analogues via epoxide opening strategy is presented. The synthesis of regioisomeric N-methyl aspidostomide D involves an efficient, five-step sequence, with 36.3% overall yield, starting from 3,4,5-tribromo-1H-pyrrole-2-carboxylic acid. The key features of this protocol are intramolecular cyclization, dehydration, oxidation, and a Lewis acid-mediated regioselective epoxide ring opening by C-3 position of 2,5-dibromo-1H-indole to furnish the title compounds.     

Total Synthesis of Siomycin A: Completion of the Total Synthesis

The total synthesis of siomycin A ( 1 ), a representative compound of the thiostrepton family of peptide antibiotics, was achieved by incorporating the five synthetic segments A ( 2 ), B ( 3 ), C ( 4 ), D ( 5 ), and E ( 6 ). The dehydropiperidine segment A ( 2 ) was esterified with the dihydroquinoline segment C ( 4 ), and the subsequent coupling with the β‐phenylselenoalanine dipeptide segment D ( 5 ) at the segment C portion followed by lactamization between the segments A and D gave segment A‐C‐D ( 27 ). This was amidated with the pentapeptide segment B ( 3 ) at the segment A portion followed by one‐pot cyclization (between segments A and B) and elongation (with the β‐phenylselenoalanine dipeptide segment E ( 6 ) at the segment A portion), thus furnishing siomycin A ( 1 ).     

Total synthesis and biological evaluation of neodysiherbaine A and analogues

Dysiherbaine (1) and its congener neodysiherbaine A (2) are naturally occurring excitatory amino acids with selective and potent agonistic activity for ionotropic glutamate receptors. We describe herein the total synthesis of 2 and its structural analogues 3-8. Advanced key intermediate 16 was employed as a branching point to assemble a series of these analogues 3-8 with respect to the C8 and C9 functionalities, which would not have been accessible through manipulations of the natural product itself. The synthesis of key intermediate 16 features (i) stereocontrolled C-glycosylation to set the C6 stereocenter, (ii) concise synthesis of the bicyclic ether skeleton through chemo- and stereoselective dihydroxylation of the exo-olefin and stereoselective epoxidation of the endo-olefin, followed by epoxide ring opening/5-exo ring closure, and (iii) catalytic asymmetric hydrogenation of enamide ester to construct the amino acid appendage. A preliminary biological evaluation of analogues for their in vivo toxicity against mice and binding affinity for glutamate receptors showed that both the type and stereochemistry of the C8 and C9 functional groups affected the subtype selectivity of dysiherbaine analogues for members of the kainic acid receptor family.     

Conformational, concomitant polymorphs of 4,4-diphenyl-2,5-cyclohexadienone: conformation and lattice energy compensation in the kinetic and thermodynamic forms

4,4-Diphenyl-2,5-cyclohexadienone (1) crystallized as four conformational polymorphs and a record number of 19 crystallographically independent molecules have been characterized by low-temperature X-ray diffraction: form A (P2(1), Z'=1), form B (P1, Z'=4), form C (P1, Z'=12), and form D (Pbca, Z'=2). We have now confirmed by variable-temperature powder X-ray diffraction that form A is the thermodynamic polymorph and B is the kinetic form of the enantiotropic system A-D. Differences in the packing of the molecules in these polymorphs result from different acidic C-H donors approaching the C=O acceptor in C-H...O chains and in synthons I-III, depending on the molecular conformation. The strength of the C-HO interaction in a particular structure correlates with the number of symmetry-independent conformations (Z') in that polymorph, that is, a short C-HO interaction leads to a high Z' value. Molecular conformation (Econf) and lattice energy (Ulatt) contributions compensate each other in crystal structures A, B, and D resulting in very similar total energies: Etotal of the stable form A=1.22 kcal mol(-1), the metastable form B=1.49 kcal mol(-1), and form D=1.98 kcal mol(-1). Disappeared polymorph C is postulated as a high-Z', high-energy precursor of kinetic form B. Thermodynamic form A matches with the third lowest energy frame based on the value of Ulatt determined in the crystal structure prediction (Cerius2, COMPASS) by full-body minimization. Re-ranking the calculated frames on consideration of both Econf (Spartan 04) and Ulatt energies gives a perfect match of frame #1 with stable structure A. Diphenylquinone 1 is an experimental benchmark used to validate accurate crystal structure energies of the kinetic and thermodynamic polymorphs separated by <0.3 kcal mol(-1) (approximately 1.3 kJ mol(-1)).     

Total synthesis of piericidin A1 and B1

The first total syntheses of piericidin A1 and B1 are disclosed and unambiguously establish the relative and absolute stereochemistry of the natural products by an approach that will facilitate the synthesis of a series of analogues. Central to the approach is an inverse electron demand Diels-Alder reaction of a N-sulfonyl-1-aza-1,3-butadiene with tetramethoxyethene followed by Lewis acid-promoted aromatization used to assemble the functionalized pyridine core. Additional key elements in the convergent approach include the use of an anti-aldol reaction to install the C9 and C10 relative and absolute stereochemistry, a modified Julia olefination for formation of the C5-C6 trans double bond with convergent assemblage of the side chain, and a penultimate heterobenzylic Stille cross-coupling reaction of the pyridyl core with the fully elaborated side chain.     

Theoretical studies of [MYR2]n isomers (M = B, Al, Ga; Y = N, P, As; R = H, CH3): structures and energetics of monomeric and dimeric compounds (n = 1, 2)

A series of group 13-15 compounds of the general formula [MYR(2)](n) (M = B, Al, Ga; Y = N, P, As; n = 1, 2; R = H, CH(3)) have been theoretically studied at the B3LYP/TZVP level of theory. The stability of different isomer structures is discussed to reveal the competitiveness of group 13-13, group 13-15, and group 15-15 bonding. Preferential bonding patterns and trends in the stability with respect to M and Y are also discussed. For the dimeric compounds, C(2v) symmetric [HMYH](2) rings are the lowest in energy, with the single exception of Ga(2)N(2)H(4), for which a somewhat unexpectedly C(2v) symmetric [GaNH(2)](2) ring is found to be the energy minimum, followed by the planar H(2)NGaGaNH(2) chain. The higher stability of the GaNH(2) bonding pattern in oligomer compounds may be rationalized in terms of the increasing stability of the oxidation state I as compared to that for the boron and aluminum analogues. Methylation significantly reduces the energetic differences between monomeric MYMe(2) MeMYMe, and Me(2)MY, isomers, especially for the AlP, AlAs, and GaAs systems, thus allowing a variety of structural types to be competitive in energy.     

Antiviral Activities of Photoactive Perylenequinones

Nine perylenequinones (PQ), including some familiar naturally occurring pigments, were compared for their light-mediated antiviral efficacies. Calphostin C was the most active compound against the two target viruses, herpes simplex virus type 1 and Sindbis virus. Hypo-crellins A and B were also very active. However, three cercosporin-like PQ were substantially less active in spite of their high quantum yields of singlet oxygen, whereas phleichrome, another efficient singlet oxygen producer, showed no detectable antiviral activity. One other PQ, which was a very weak singlet oxygen producer, also showed no antiviral activity. None of the active compounds showed significant antiviral activity in the dark. Thus, for some groups of PQ there was correlation between quantum yield of singlet oxygen C0₂) and antiviral efficacy, but there are evidently other structural features of PQ that influence activity.     

Asymmetric synthesis of a chiral diarsine ligand via a cycloaddition reaction between 3,4-dimethyl-1-phenylarsole and diphenylvinylarsine

The organopalladium complex containing ortho-metallated (S)-[1-(dimethylamino)ethyl]naphthalene as a chiral auxiliary has been successfully employed to promote the asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylarsole and diphenylvinylarsine. In the intramolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 6:1. The chiral naphthylamine auxiliary could be removed chemoselectively from the template by treatment with HCl and subsequently NaI to generate the neutral diiodo complex [(As–As)PdI₂]. Treatment of the diiodo complex with KCN gave the enantiomerically pure As–As bidentate ligand in quantitative yield. In contrast to the reported similar P–P and As–P analogues, both arsenic donors in the diiodo complex could be readily eliminated to produce a structurally novel dimetallic complex.     

Oligonucleotide Analogues with a ‘Nucleobase‐Including Backbone’. Part 10

The dinucleoside analogues 24, 25, 28 – 30 , and 33 associate in CDCl₃ solution. Association constants, as determined from the concentration‐dependent chemical shift for H? N(3) of the uridine moiety and from thermodynamic parameters, range from 265 M ^?1 ( 33 ) to 3220 M ^?1 ( 30 ). The association of 31 in CDCl₃ is too strong to be determined (concentration independent δ(H? N(3)) of ca. 12.8 ppm) and the fully deprotected dimer 32 proved insufficiently soluble in CDCl₃. This observation strongly evidences that structural differentiation of oligonucleotides and their analogues into backbone and nucleobases is not required for pairing. The dinucleotide analogues were prepared by O‐alkylation of C(8)‐unsubstituted or of C(8)‐oxymethylated, partially protected adenosines by the C(6)‐mesyloxy‐ or C(6)‐halomethylated uridines 20 – 22 , followed by partial or total deprotection.     

Structural-electronic correlation in the first-order phase transition of [FeH2L2-Me](ClO4)2 (H2L2-Me = bis[((2-methylimidazol-4-yl)methylidene)-3- aminopropyl]ethylenediamine)

The synthesis and detailed study of the new mononuclear spin crossover complex [Fe(II)H2L(2-Me)](ClO4)2 (where H2L(2-Me) = bis[((2-methylimidazol-4-yl)methylidene)-3-aminopropyl]ethylenediamine) are reported. Variable-temperature magnetic susceptibility measurements show the occurrence of a steep spin crossover centered at 171.5 K with a hysteresis loop of ca. 5 K width (T(/2)(increasing) = 174 K and T(1/2)(decreasing) = 169 K, for increasing and decreasing temperatures, respectively). The crystal structure has been resolved for the high-spin (HS) and low-spin (LS) states at 200 and 123 K, respectively, revealing a crystallographic phase transition that occurs concomitantly to the spin crossover: at 200 K, the complex crystallizes in the monoclinic system, space group P2(1)/n, while the space group is P2(1) at 123 K. The mean Fe-N distances are shortened by 0.2 A, but the thermal spin crossover is accompanied by significant structural changes: the rearrangement of the central atom C12 of a six-membered chelate ring of [Fe(II)H2L(2-Me)]2+ to two positions (C12A and C12B) and, consequently, the lack of an inversion center at 123 K (P2(1) space group). Both HS and LS supramolecular structures involve all possible hydrogen bonds between imidazole and amine NH functions, and perchlorate anions; however, the HS supramolecular structure is a one-dimensional (1D) network, and the LS phase may better be described as a two-dimensional (2D) extended structure of A and B molecules. The structural phase transition of [FeH2L(2-Me)](ClO4)2 seems to trigger the steep and hysteretic spin crossover. Discontinuities in the temperature dependence of the M?ssbauer parameters (isomer shift and quadrupole splitting) at the spin crossover temperature confirmed the occurrence of a structural phase transition. The experimental enthalpy and entropy variations were determined by differential scanning calorimetry (DSC) as 7.5 +/- 0.4 kJ/mol and 45 +/- 3 J K(-1) mol(-1), respectively. The regular solution theory was applied to the experimental data, yielding an interaction parameter of Gamma = 3.36 kJ/mol, which is larger than 2RT(1/2), which fulfills the condition for observing hysteresis.     

Metal-induced B-H activation: addition of acetylene, propyne, or 3-methoxypropyne to Rh(Cp*), Ir(Cp*), Ru(p-cymene), and Os(p-cymene) half-sandwich complexes containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolato ligand

The addition reactions of the 16e half-sandwich complexes [M(eta5-Cp*)[E2C2(B10H10)]] (Cp*=pentamethylcyclopentadienyl: 1S: E=S, M=Rh; 2S: E=S; M=Ir; 2Se: E=Se, M=Ir) and [M(eta6-p-cymene)[S2C2(B10H10)]] (p-cymene=4-isopropyltoluene; 3S: M=Ru; 4S: M=Os), with acetylene, propyne, and 3-methoxypropyne lead to the 18e complexes 5-19 with a metal-boron bond in each case. The reactions start with an insertion of the alkyne into one of the metal-chalcogen bonds, followed by B-H activation, transfer of one hydrogen atom from the carborane via the metal to the terminal carbon of the alkyne, and concomitant ortho-metalation of the carborane. The E-eta2-CC and the C(1)B units are arranged either cisoid or transoid at the metal. X-ray structural analyses are reported for one of the starting 16e complexes (4S), the cisoid complex 12S (from 2S and HC[triple bond]C-CH3), and the transoid complexes 9S and 14S (from 1S and HC[triple bond]C-CH2OMe, and from 3S and HC[triple bond]CH, respectively). All new complexes 5-19 were characterized by NMR spectroscopy (1H, 11B, 13C, and 77Se and 103Rh NMR spectroscopy when appropriate).     

Pd-catalyzed carbocyclization-Negishi cross-coupling cascade: a novel approach to 1alpha,25-dihydroxyvitamin D3 and analogues

[reaction: see text] A mild palladium-catalyzed cascade has been used for the synthesis of the hormone 1alpha,25-dihydroxyvitamin D3 (calcitriol, 1a) and its analogues 1b and 1c. This one-pot process involves two consecutive transformations at room temperature: An initial palladium-catalyzed 6-exo-cyclocarbopalladation of vinyl triflates followed by a Negishi cross-coupling reaction with an alkenyl zinc. This novel strategy opens new possibilities for the preparation of a variety of new vitamin D analogues of therapeutic potential, particularly with modifications at the triene and/or ring-A.     

Total synthesis and structural elucidation of azaspiracid-1. Final assignment and total synthesis of the correct structure of azaspiracid-1

The molecular structure of azaspiracid-1, a neurotoxin isolated from mussels, has been elucidated by total synthesis which also enriched its supplies. The degradatively derived fragments of this marine biotoxin, compounds 5 (EFGHI), 6 (FGHI), and 40 (ABCD), were matched with synthetic materials, thus confirming their structural identities. Based on this detective work, a new structure of azaspiracid-1 (i.e., 1) was proposed and constructed by total synthesis. The final strategy for the total synthesis of azaspiracid-1 featured a dithiane anion (C(21)-C(27) fragment) reacting with a pentafluorophenol ester (C(1)-C(20) fragment) followed by a Stille-type union of an advanced allylic acetate substrate (C(1)-C(27) fragment) with a vinyl stannane as the main coupling processes to assemble the carbon skeleton of the molecule. In addition to the total synthesis of azaspiracid-1 (1), the syntheses of its C(1)-C(20) epimer (2) and of several truncated analogues for biological investigations are described.     

Total synthesis of everninomicin 13,384-1--Part 1: retrosynthetic analysis and synthesis of the A1B(A)C fragment

In this first of a series of four articles we introduce everninomicin 13,384-1 (1), a powerful antibiotic effective against drug resistant bacteria, as a target for total synthesis and discuss its retrosynthetic analysis. From the three defined fragments required for the synthesis (2: A1B(A)C fragment; 4: DE fragment; 5: FGHA2 fragment), we describe herein two approaches to the A1B(A)C block. The first strategy relied on an olefin metathesis reaction to construct a common intermediate for rings B and C, but was faced with final protecting group problems. The second, and successful approach, involved a 1,2-phenylsulfeno migration and a sulfur directed glycosidation procedure to link rings B and C, as well as an acyl fluoride intermediate to install the sterically hindered aryl ester moiety (ring A1). The final stages of the synthesis of the required 2-phenylseleno glycosyl fluoride 2 required introduction of a phenylseleno group at C-1 of ring C followed by a novel, DAST-promoted 1,2-migration to produce the desired 2-beta-phenylseleno glycosyl fluoride moiety.