Showing papers by "George M. Whitesides published in 1986"

Preparation of optically active 1,2-diols and α-hydroxy ketones using glycerol dehydrogenase as catalyst: limits to enzyme-catalyzed synthesis due to noncompetitive and mixed inhibition by product.

Abstract: Glycerol dehydrogenase (GDH, EC 1.1.1.6, from Enterobacter aerogenes or Cellulomonas sp.) catalyzes the interconversion of analogues of glycerol and dihydroxyacetone. Its substrate specificity is quite different from that of horse liver alcohol dehydrogenase (HLADH), yeast alcohol dehydrogenase, lactate dehydrogenase, and other alcohol dehydrogenases used in enzyme-catalyzed organic synthesis and is thus a useful new enzyrnic catalyst for the synthesis of enantiomerically enriched and isotopically labeled organic molecules. This paper illustrates syrthetic applications of GDH as a reduction catalyst by the enantioselective reduction of 1-hydroxy-2-propanone and 1-hydroxy-2-butanone to the corresponding fi 1,2-diols (ee = 95-98%). (R)-1,2-Butanediol-2-d1 was prepared by using formate-d1 as the ultimate reducing agent. Comparison of (R)-1,2-butanediol prepared by reduction of 1-hydroxy-2-butanone enzymatically and with actively' fermenting bakers' yeast indicated that yield and enantiomeric purity were similar by the two procedures. Reactions prcrceeding in the direction of substrate oxidation usually suffer from slow rates and incomplete conversions due to product inhibition. The kinetic consequences of product inhibition (competitive, noncompetitive, and mixed) for practicai synthetic applications of GDH, HLADH, and other oxidoreductases are analyzed. In general, product inhibition seems the most serious limitation to the use of these enzymes as oxidation catalysts in organic synthesis.

Fluorescence properties of dansyl groups covalently bonded to the surface of oxidatively functionalized low-density polyethylene film

Abstract: : Brief oxidation of low-density polyethylene film with chromic acid in aqueous sulfuric acid introduced carboxylic acid and ketone and/or aldehyde groups onto the surface of the film. The carboxylic acid moieties can be used to attach more complex functionality to the polymer surface. We are developing this surface-functionalized polyethylene (named 'polyethylene carboxylic acid,' PE-CO2H, to emphasize the functional group that dominates its surface properties) as a substrate with which to study problems in organic surface chemistry--especially wetting, polymer surface reconstruction, and adhesion--using physical-organic techniques. This document describes the preparation, characterization, and fluorescence properties of derivatives of PE-CO2H in which the Dansyl (5-dimethylaminonaphthalene-1-sulfonyl) group has been covalently attached by amide links to the surface carbonyl moieties. Keywords: Acidity; and Solvent effects.

cis-[Bis(dicyclohexylphosphino)ethane]platinum(0) reacts with unactivated carbon-hydrogen bonds

Abstract: Although platinum(0) is centrally important in heterogeneous catalytic reforming of petroleum, the only soluble platinum complexes that react with saturated hydrocarbons are platinum chlorides and acetates. In particular, and by contrast with iridium, rhodium, and the other transition metals that have provided the basis for the recent major advances in carbon-hydrogen bond activation, no phosphine-stabilized platinum species has been reported that reacts intermolecularly with unactivated C-H bonds, although intramolecular reaction is facile. Here, the report that thermal reductive elimination of neopentane from cis-hydrido-neopentyl(bis(dicyclohexylphosphino)ethane)platinum(II) (1) produces the reactive intermediate (bis(dicyclohexylphosphino)-ethane)platinum(0) (2) and that 2 reacts with C-H bonds in saturated and unsaturated hydrocarbons.

Radical isomerization during Grignard reagent formation. A quantitative treatment.

Abstract: ( l ) (a) Walborsky, H.M.; Young, A. E. J. Am. Chem. Soc. 1961,83, 2595. (b) Walborsky, H. M.; Young, A. E. J. Am. Chem. Soc. 1964, 86,3288. (c) Wafborsky, H. M.; Aronoff, M. S. \"/. Organomet. Chem. 1973, 5i,,31. (d) Walborsky, H. M.; Banks, R. B. Bul / . Soc. Chim. Belg.1980,89,849. (2) Ruchardt , C. ; Trautwein, H. Chem. Ber. 1962,95, 1197. (3) Patel , D. J. ;Hami l ton, C. L. ;Roberts, J.D. J. Am. Chem. Soc. 1965, 8 7 , 5 1 4 4 . (4) (a) Lamb, R. C. ; Ayers, P. W.; Toney, M. K. ; Garst , J :F. J. Am. Chem. Soc. 1966, 88,4261. (b) Walling, C.; Cioffari, A. ,/. Am. Chem. Soc. t970 .92 .6609 . (5) (a) Grootveld, H. H.; Blomberg, C.; Bickelhaupt, F. Tetrahedron Lett. 1971, 1999. (b) Bodewitz, H. W. H. J.; Blomberg, C.; Bickelhaupt, F. Tetrahedron Lett. 1972,251. (c) Bodewitz, H. W. H. J.; Blomberg, C.; Bickelhaupt, F. Tetrahedron 1973, 29,719. (d) Bodewitz, H. W. H. J.; Blomberg, C.; Bickelhaupt, F. Tetrahedron 1975,3/,,1053. (e) Schaart, B. J.; Bodewitz, H. W. H. J.; Blomberg, C.; Bickelhaupt, F. J. Am. Chem, Soc. 1976, 98, 3712. (n Bodewitz, H. W. H. J. ; Schaart , B. J. ; Van der Met, J . D.; Blomber, C.; Bickelhaupt, F.; Den Hollander, J. A. Tetrahedron 1978, 34, 2523. (6) Buske, G. R.; Ford, W. T. J. Org. Chem. 1976, 41, 1998. (7) Grovenstein, E.; Cottingham, A. B.; Gelbaum, L. T. J. Org. Chem. 1978, 43,3332. (S) (a) Rogers, H. R. ; Hi l l , C. H. ; Fuj iwara, Y. ; Rogers, R. J. ; Mi tcheU, H. L. ; Whi tesides. G. M. J. Am. Chem. Soc. 1980, 102,217. (b) Rogers, H. R.: Deutch, J. ; Whi tesides, G. M. J. Am. Chem. Soc. 1980, 102,226. (c) Rogers, H. R.; Rogers, R. J.; Mitchell, H. L.; Whitesides, G. M. J. Am. Chem. Soc. 1980, 102,231. (d) Lawrence, L. M.;Whitesides, G. M. '/. Am. Chem. Soc. 1980. 102,2493. (e) Root, K. S. Deutch, J.; Whitesides, G. M. J. Am. Chem. Soc . 1981 , 103 ,5475 . (9) (a) Dubois, J. E.; Molle, G.;Touril lon, G.; Bauer, P. Tetrahedron lrtt. 1979, 5069. (b) Molle, G.; Bauer, P.; Dubois, J. E. J. Org. Chem. 1982, 47, 4120. (10 ) Gr i l l e r , D . ; I ngo ld , K . l J . Acc . Chem. Res . 1980 , 13 ,31 '1 .

Improved adhesion of thin conformal organic films to metal surfaces

Abstract: A technique is described for attaching thin, conformal, pin‐hole‐free electrically insulating polyethylene films to flat gold surfaces (previously modified by adsorption of a monolayer of an organic disulfide) by plasma polymerization. These polyethylene films are tough enough to support the attachment of gold electrodes.

Glycerol Kinase: Substrate Specificity.

Abstract: Glycerol kinase (8.C. 2.7.1.30, ATP: glycerol-3-phosphotransferase) catalyzes the phosphorylation of 28 nitrogen, sulfur, and alkyl-substituted of glycerol. A survey of 66 analogues has defined qualitatively the structural characteristics nffissary for acceptability as a substrate by this enzyme. This survey was conducted using an assay based on 3lP NMR spectroscopy which detected products produced even by slow reactions. These studies indicate that glycerol kinase accepts a range of substituents in place of one terminal hydroxyl group (that which is not phosphorylated), and that the hydrogen atcm atC-2 can be replaced by a methyl group. Replacement of the second terminal hydroxyl group (that which is normally phosphorylated) by other nucleophilic centers usually results in loss of activity. Glycerol kinase is a useful catalyst for the synthesis of chiral organic substances, especially starting materials for the preparation of phospholipids and analogues. Comparisons of kinetic constants for enzymes from four microorganisms (Candida mycoderma, Saccharomyces cereuisiae, Escherichia coli, and Bacillus stearothermophilus) indicate little variation among them. All phosphorylated products have stereochemistry analogous to that of sn-glycerol- 3-phosphate.

Novel hydroperoxide and use of same as intermediate for the preparation of 3a,6,6,9a-tetramethylperhydronaphtho(2,1-b)furan

Abstract: Novel hydroperoxide of formula ##STR1## and use of same as intermediate for the preparation of 3a,6,6,9a-tetramethylperhydronaphtho[2,1-b]furan, also known as AMBROX (registered tradename of FIRMENICH SA, Geneva/Switzerland). Process for its preparation via an oxidation of sclareol by means of hydrogen peroxide in the presence of an acidic agent.

Process for the preparation of hydroperoxide compounds, compounds of this type and their use as intermediates for the preparation of 3a,6,6,9a-tetramethylperhydronaphtho[2,1-b]furan

Abstract: Epimeric hydroperoxides of the formula in the isolated state or as a mixture, are used as an intermediate for the preparation of AMBROX. The compounds (I) are obtained by reaction of sclareol with hydrogen peroxide in the presence of an acidic agent. They are converted to AMBROX by treatment with a redox pair consisting of Fe /Cu .

Mechanisms of Thermal Decomposition of tra ns-Chloroneopentylbis (tricyclopentylphosphine ) platinum ( I I ) t

Abstract: The most probable mechanism for the thermal decomposition