High Trans Research Articles

Vibrational spectra and potential energy distributions of normal modes of 3-nitroso- and 3-nitrocyclopropenes

The structural stability of 3-nitrosocyclopropene c-C 3H 3–NO and 3-nitrocyclopropene c-C 3H 3–NO 2 was investigated by density functional B3LYP and ab initio MP2 calculations using 6-311+G ∗∗ basis set. From the calculation, 3-nitrosocyclopropene was predicted to exist predominantly in the trans conformation (NO bond is trans to the ring and eclipse α-hydrogen of the ring) with high trans– cis rotational barrier of about 8 kcal/mol. The NO 2 rotational barrier in 3-nitrocyclopropene was predicted from the symmetric potential scan to be of about 4.4 kcal/mol. The vibrational frequencies were computed at DFT-B3LYP/6-311+G ∗∗ level for both molecules. Normal coordinate calculations were carried out and potential energy distributions were calculated for the two molecules.

Stereoselective cyclopropanation by cyclocopolymerization of butadiene.

An unprecedented cyclopropanation by cyclopolymerization reaction is presented. In particular, catalytic copolymerization processes of ethene and butadiene lead with high trans selectivity to a complete cyclocopolymerization of butadiene units. Ethene-based copolymers including cyclopropane and cyclopentane rings, which can be relevant to polyolefin applications, are obtained with high yields. Several aspects relative to the mechanism of this cyclocopolymerization reaction, including the high stereoselectivity, are discussed.

Trans Fatty Acids in Margarines Marketed in Eleven Countries.

Determination was made of trans fatty acid content in margarines marketed in Austria, Belgium, Czech Republic, Denmark, Finland, Hungary, Japan, Norway, Poland, Sweden and the United States by gas-liquid and silver-ion thin-layer chromatography carried out in conjunction. As wt% of total fatty acid, it was found that, in print margarines, trans fatty acid was less than 3% in most products of Austria, Finland, Hungary and Sweden. For products of Belgium, trans fatty acid was relatively low, at 4% on the average. In Czech Republic and Denmark, trans fatty acid was divided into two groups of less than 2% and 20% or more. In Japan, Norway, Poland and the United States, trans fatty acid was found to exceed 20%. In tub margarines, trans fatty acid was generally below 3% for Austria, Belgium, Czech Republic, Denmark, Finland, Hungary and Sweden. Japan, Norway, Poland and the United States indicated mean trans fatty acid to be relatively high, at 13-16%, though several brands of low trans fatty acid margarines (below 3%) appear on the market in these countries. In most cases, margarines low in trans fatty acid were rich in saturated fatty acid and the total value of trans and saturated fatty acids (TFA+SFA) was essentially the same in high and low trans fatty acid margarines. Margarines with total cis-polyunsaturated fatty acid (PUFA) to TFA+SFA ratio [PUFA/(TFA+SFA)], above 1, are available as print margarines in Denmark and tub margarines in all the other countries except for Sweden. TFA+SFA content (g/100g) in print margarines in the United States was quite low and tub margarines in Japan were noted to contain considerable TFA+SFA.

Dietary trans fatty acids in early life: a review.

Trans fatty acids are unsaturated fatty acids with at least a double trans configuration, resulting in a more rigid molecule close to a saturated fatty acid. These appear in dairy fat because of ruminal activity, and in hydrogenated oils; margarines, shortenings and baked goods contain relatively high levels of trans fatty acids. These fatty acids can be incorporated into both fetal and adult tissues, although the transfer rate through the placenta continues to be a contradictory subject. In preterm infants and healthy term babies, trans isomers have been inversely correlated to infantile birth weight. However, in multigenerational studies using animals, there is no correlation between birth weight, growth, and dietary trans fatty acids. Maternal milk reflects precisely the daily dietary intake of trans fatty acids, from 2% to 5% of the total fatty acids in human milk. The level of linoleic acid in human milk is increased by a high trans diet, but long-chain polyunsaturated fatty acids remain mostly unaffected. Likewise, infant tissues incorporate trans fatty acids from maternal milk, raising the level of linoleic acid and relatively decreasing arachidonic and docosahexaenoic acids. This suggests an inhibitory effect of trans fatty acid on liver Delta-6 fatty-acid desaturase activity. As opposed to blood and liver, the brain appears to be protected from the trans fatty-acid accumulation in experimental animals, but no data have yet been reported for human newborns. Further investigations in humans are needed to definitively establish the potential physiological consequences of trans fatty-acid intake during the neonatal period.

Hydrogenated fat consumption affects acylation-stimulating protein levels and cholesterol esterification rates in moderately hypercholesterolemic women

To determine whether hydrogenated fat consumption alters triglyceride metabolism and cholesterol esterification rates, 14 women (65–71 years of age) were provided with each of four diets for 5-week periods according to a randomized cross-over design. The experimental diets contained either soybean oil (SO), low trans squeeze (SQM), medium trans tub (TM), or high trans stick (SM) margarines. Triglyceride uptake by adipose tissue was determined by measuring plasma acylation-stimulating protein (ASP), FFA, glucose, and insulin levels, while rates of transfer and esterification rate of newly synthesized cholesterol (ER) were derived by using plasma CETP levels and the deuterium incorporation methodology. Plasma ASP levels were lowest (P < 0.05) in subjects on the SM diet (33.4 ± 12.7 nM) compared with the SO (48.7 ± 17.0 nM) and SQM (50.7 ± 15.7 nM) diets. Conversely, FFA were highest (P < 0.05) on the SM diet (0.86 ± 0.45 mM) relative to all the other diets. No differences were observed in plasma glucose and insulin levels among diets. A trend toward higher CETP levels after consumption of the SM diet was observed. However, the ER was lowest (P < 0.05) after the SM (0.111 ± 0.062 g·day−1) diet and highest after consumption of the SQM (0.216 ± 0.123 g·day−1) diet. In addition, ASP levels were negatively correlated with FFA (r = −0.63, P < 0.05), LDL cholesterol (r = −0.56, P < 0.05), and TG (r = −0.41, P < 0.05), whereas FFA was positively correlated with apolipoprotein B-containing lipoproteins (r = 0.58 and 0.47, for VLDL and LDL cholesterol, P < 0.05), and negatively correlated with HDL cholesterol (r = −0.51, P < 0.05). The ER was found to positively correlate with HDL cholesterol and HDL2 subfraction (r = 0.53 and 0.45, respectively, P < 0.05). Taken together, these data demonstrate that the alterations in circulating lipid levels, commonly observed with consumption of hydrogenated fat-rich diets, can be explained in part by changes in ASP activity as well as newly synthesized cholesterol ER.—Matthan, N. R., K. Cianflone, A. H. Lichtenstein, L. M. Ausman, M. Jauhiainen, and P. J. H. Jones. Hydrogenated fat consumption affects acylation-stimulating protein levels and cholesterol esterification rates in moderately hypercholesterolemic women.

Conformation and Dynamics of Atactic Poly(acrylonitrile). 2. Torsion Angle Distributions in Meso Dyads from Two-Dimensional Solid-State Double-Quantum 13C NMR

The average trans torsion angles and their distributions have been investigated for meso dyads in a disordered crystalline polymer, atactic poly(acrylonitrile) (aPAN), by two-dimensional (2D) solid-state 13C double-quantum NMR spectroscopy (DOQSY). The 2D DOQSY spectra of an aPAN sample with 13C-labeled nitrile side groups show significant deviations from the ideal trans conformations. The 13C⋮N bonds in meso trans−trans dyads make an average angle of 20° with each other, with distributions of 25° standard deviation. This translates into standard deviations of σ = 20° for the two successive torsion angles in these dyads. The experimental spectrum constrains the average torsion angles to a line between (+160 ± 10°, +160 ± 10°) and (±170 ± 5°, ∓170 ± 5°), with distributions of standard deviation σ = 20 ± 5° for both torsion angles. It is also confirmed that the trans:gauche ratio of backbone bonds in aPAN is 90:10 (±5%). The high trans content is apparently enabled by the torsion angle deviations from the ideal trans state in meso trans−trans dyads, which alleviate the steric hindrance and the large electric dipole interaction between the CN groups and thus lower the intramolecular conformational energy.

ChemInform Abstract: Extremely High trans Selectivity of Ti‐MWW in Epoxidation of Alkenes with Hydrogen Peroxide.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Stereoselective reductive radical cyclization of ketonitriles catalyzed by Cp2TiCl2 in the presence of chlorosilane and zinc

Reductive radical cyclization of ketonitriles was catalyzed by Cp2TiCl2 in the presence of Me3SiCl, zinc powder and imidazole, giving the 2-amino-3-cyano-2-cyclopenten-1-ols in moderate to good yields with high trans selectivity (up to 94% trans). The influence of the catalyst, chlorosilane, co-reductant, solvent, and temperature on both the yield and diastereoselectivity of the cyclized products was investigated in detail.

Dietarytrans α-linolenic acid does not inhibit Δ5- and Δ6-desaturation of linoleic acid in man

Dietary trans monoenes have been associated with an increased risk of heart disease in some studies and this has caused much concern. Trans polyenes are also present in the diet, for example, trans α-linolenic acid is formed during the deodorisation of α-linolenic acid-rich oils such as rapeseed oil. One would expect the intake of trans α-linolenic acid to be on the increase since the consumption of rapeseed oil in the western diet is increasing. There are no data on trans α-linolenic acid consumption and its effects. We therefore carried out a comprehensive study to examine whether trans isomers of this polyunsaturated fatty acid increased the risk of coronary heart disease. Since inhibition of A6-desaturase had also been linked to heart disease, the effect of trans α-linolenic acid on the conversion of [U- 13 C]-labelled linoleic acid to dihomo-γ-linolenic and arachidonic acid was studied in 7 healthy men recruited from the staff and students of the University of Edinburgh. Thirty percent of the habitual fat was replaced using a trans free'- or 'high' trans α-linolenic acid fat. After at least 6 weeks on the experimental diets, the men received 3-oleyl, 1,2-[U- 13 C]-linoleyl glycerol (15 mg twice daily for ten days). The fatty acid composition of plasma phospholipids and the incorporation of 13 C-label into n-6 fatty acids were determined at day 8, 9 and 10 and after a 6-week washout period by gas chromatography-combustion-isotope ratio mass spectrometry. Trans α-linolenic acid of plasma phospholipids increased from 0.04 ± 0.01 to 0.17 ± 0.02 and cis α-linolenic acid decreased from 0.42 ± 0.07 to 0.29 ± 0.08 g/100 g of fatty acids on the high trans diet. The composition of the other plasma phospholipid fatty acids did not change. The enrichment of phosphatidyl 13 C-linoleic acid reached a plateau at day 10 and the average of the last 3 days did not differ between the low and high trans period. Both dihomo-γ-linolenic and arachidonic acid in phospholipids were enriched in 13 C, both in absolute and relative terms (with respect to 13 C-linoleic acid). The enrichment was slightly and significantly higher during the high trans period (P L'effet d'un regime alimentaire enrichi en acide trans α-linolenique, du par exemple a l'augmentation de la consommation d'huile de colza, a ete etudie chez 7 hommes volontaires et sains, le but etant de demontrer si la consommation accrue de l'isomere trans de cet acide gras polyinsature augmente le risque de cardiopathie coronaire. Comme l'inhibition de l'enzyme Δ6-desaturase a egalement ete liee a ce risque cardiovasculaire, l'effet de l'acide trans α-linolenique sur la conversion de l'acide linoleique en dihomo-γ-linolenique et acide arachidonique a ete etudie, en dosant la composition en acide gras des phospholipides plasmatiques. Les resultats suggerent que ce regime alimentaire riche en acide trans α-linolenique n'inhibe pas la conversion de l'acide linoleique.

Dietary trans α-linolenic acid does not inhibit Δ5- and Δ6-desaturation of linoleic acid in man

Dietary trans monoenes have been associated with an increased risk of heart disease in some studies and this has caused much concern. Trans polyenes are also present in the diet, for example, trans α-linolenic acid is formed during the deodorisation of α-linolenic acid-rich oils such as rapeseed oil. One would expect the intake of trans α-linolenic acid to be on the increase since the consumption of rapeseed oil in the western diet is increasing. There are no data on trans α-linolenic acid consumption and its effects. We therefore carried out a comprehensive study to examine whether trans isomers of this polyunsaturated fatty acid increased the risk of coronary heart disease. Since inhibition of Δ6-desaturase had also been linked to heart disease, the effect of trans α-linolenic acid on the conversion of [U-13C]-labelled linoleic acid to dihomo-γ-linolenic and arachidonic acid was studied in 7 healthy men recruited from the staff and students of the University of Edinburgh. Thirty percent of the habitual fat was replaced using a trans ‘free’- or ‘high’ trans α-linolenic acid fat. After at least 6 weeks on the experimental diets, the men received 3-oleyl, 1,2-[U-13C]-linoleyl glycerol (15 mg twice daily for ten days). The fatty acid composition of plasma phospholipids and the incorporation of 13C-label into n-6 fatty acids were determined at day 8, 9 and 10 and after a 6-week washout period by gas chromatography-combustion-isotope ratio mass spectrometry. Trans α-linolenic acid of plasma phospholipids increased from 0.04 ? 0.01 to 0.17 ? 0.02 and cis ? -linolenic acid decreased from 0.42 ? 0.07 to 0.29 ? 0.08 g/100 g of fatty acids on the high trans diet. The composition of the other plasma phospholipid fatty acids did not change. The enrichment of phosphatidyl 13C-linoleic acid reached a plateau at day 10 and the average of the last 3 days did not differ between the low and high trans period. Both dihomo-γ-linolenic and arachidonic acid in phospholipids were enriched in 13C, both in absolute and relative terms (with respect to 13C-linoleic acid). The enrichment was slightly and significantly higher during the high trans period (P<0.05). Our data suggest that a diet rich in trans α-linolenic acid (0.6% of energy) does not inhibit the conversion of linoleic acid to dihomo-γ-linolenic and arachidonic acid in healthy middle-aged men consuming a diet rich in linoleic acid.

Influence of the pentaamine skeleton on the nitrito to nitro isomerization reactions on complexes of cobalt(III)

The nitrito to nitro spontaneous isomerization reaction of the complexes [Co(MeNH 2) 5(ONO)] 2+, cis-[Co(MeNH 2)(NH 3) 4(ONO)] 2+, trans-[Co(MeNH 2)(NH 3) 4(ONO)] 2+, trans-[Co(en) 2(NH 3)(ONO)] 2+, trans-[Co(en) 2(MeNH 2)(ONO)] 2+, trans-[CoL 14(ONO)] 2+ and cis-[CoL 14(ONO)] 2+ has been studied as a function of temperature and pressure. The corresponding base-catalyzed reactions of the systems with monodentate ligands have also been studied as a function of temperature and pressure. The results produce thermal and baric activation parameters that can be as a whole related to an ordered expansion to go to the transition state. This is particularly true for the (N) 5 macrocyclic L 14 systems (L 14=6-methyl-1,4,8,11-tetraazacyclotetradecane-6-amine) where the importance of hydrogen bonding becomes evident as for related studies. For systems with a high trans influence the results indicate a clear increase of the degree of dissociation to go to the transition state, very much in line with what has been observed for previously studied substitution reactions. Thus, the results agree with the fact that the nitrito to nitro isomerization reactions, in spite of being of intramolecular nature as established by very clear results, follow a reactivity pattern very similar to that observed for the substitution reactions of neutral ligands on the same complexes. That is, the transition state of the process has a high resemblance to that of the dissociatively activated substitution reactions of the Co(III) complexes.

Selective hydrogenation of sunflower seed oil in a three‐phase catalytic membrane reactor

AbstractContinuous hydrogenation of sunflower seed oil has been carried out in a novel three‐phase catalytic membrane hydrogenation reactor. The membrane reactor consisted of a membrane impregnated with Pd as the active catalyst, which provided a catalytic interface between the gas phase (H2) and the oil. Hydrogenations were carried out at different pressures, temperatures, and selectivities, and the formation of trans isomers was monitored during the hydrogenation runs. For the three‐phase catalytic membrane reactor, interfacial transport resistances and intraparticle diffusion limitations did not influence the hydrogenation reaction. Hydrogenation runs under kinetically controlled conditions showed that oleic and elaidic acid were not hydrogenated in the presence of linoleic acid. Initial formation of stearic acid was caused by direct conversion of linoleic acid into stearic acid by a shunt reaction. Furthermore, high selectivities led to high trans levels, which is in accordance with the many published data on hydrogenation of vegetable oils in slurry reactors. Finally, the catalytic membrane showed severe catalyst deactivation. Only partial recovery of the catalyst activity was possible.

Study of structural stability and vibrational spectra of nitroso and nitroketenes

The structural stability of nitrosoketene and nitroketene was investigated using ab initio calculations. The calculations were carried out at DFT-B3LYP/6-311++G ∗∗ level. From the calculation the molecules were predicted to exist predominantly in the planar conformations. Nitrosoketene was predicted to exist predominantly in the trans conformation with high trans– cis rotational barrier. The rotational barrier of the NO group in nitrosoketene was calculated to be about 18 kcal/mol, while that of the NO 2 group in nitroketene to be about 10 kcal/mol. The vibrational frequencies were computed, normal coordinate calculations were carried out and potential energy distributions were calculated for both molecules.

Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study: a prospective population-based study

Evidence on the relation between trans fatty acid intake and coronary heart disease is limited. We investigated this relation in a Dutch population with a fairly high trans fatty acid intake, including trans fatty acids from partly hydrogenated fish oils. We prospectively studied 667 men of the Zutphen Elderly Study aged 64-84 years and free of coronary heart disease at baseline. We used dietary surveys to establish the participants' food consumption patterns. Information on risk factors and diet was obtained in 1985, 1990, and 1995. After 10 years of follow-up from 1985-95, there were 98 cases of fatal or non-fatal coronary heart disease. Between 1985 and 1995, average trans fatty acid intake decreased from 4.3% to 1.9% of energy. After adjustment for age, body mass index, smoking, and dietary covariates, trans fatty acid intake at baseline was positively associated with the 10-year risk of coronary heart disease. The relative risk for a difference of 2% of energy in trans fatty acid intake at baseline was 1.28 (95% CI 1.01-1.61). A high intake of trans fatty acids (all types of isomers) contributes to the risk of coronary heart disease. The substantial decrease in trans fatty acid intake, mainly due to industrial lowering of trans contents in Dutch edible fats, could therefore have had a large public-health impact.

Conformational Changes of the Noncrystalline Chains for Syndiotactic Polypropylene as a Function of Temperature: Correlations with the Crystallizations of Form I and Form III

The conformation and molecular mobility of the noncrystalline chains for syndiotactic polypropylene (sPP) samples well crystallized have been characterized at different temperatures by high-resolution solid-state 13 C NMR spectroscopy. The purposes are to investigate the cause inducing the high trans fraction of sPP chains in the noncrystalline state just after quenched at 0 °C from the melt and to know some correlation with the crystallization of form III with the planar zigzag conformation around 0 °C. Two samples containing form I and III crystallites were respectively crystallized at 100 °C for 24 h and at 0 °C for 144 h from the melt, their degrees of crystallinity being 0.60 and 0.31. A new line shape analysis for the CH 2 resonance line confirms in good accord with the previous analysis for the CH 3 line that the trans fraction is of the high level of 0.80 in the noncrystalline state just after quenched at 0 °C from the melt. The trans fraction is also determined for the noncrystalline components in the form I and III samples as a function of temperature by the line shape analysis for the CH 3 resonance line. As a result, it is found that there are three temperature regions, regions A, B, and C, where the trans fractions are greatly different. In region A below 15 °C, the trans fraction is as high as 0.73-0.80, and it seems to significantly depend on the degree of crystallinity. In contrast, this fraction is as low as about 0.57 in region C above 60 °C, in good accord with the level at the melt. In region B at 15-60 °C, the trans fraction drastically changes as is possibly named as trans-rich chain assembly-coiled chains transition. However, no significant conformational change is observed for the results obtained at different temperatures by the similar analysis for the CH 2 resonance line, suggesting the preferable production of some conformations mainly due to the steric hindrance between the CH 3 groups including the second and third neighbors. 13 C spin-spin relaxation measurements for the noncrystalline component in the form I sample also reveal that the molecular motion is highly limited in regions A and B even above Tg while the rubberlike mobility is allowable in region C. On the basis of these experimental results and the previous results of the preferential crystallizations of forms I and III in these regions, some factors affecting these crystallizations are discussed.

Density functional calculation of N–N barrier and analysis of vibrational spectra for nitrosoisocyanate and nitroisocyanate

The structural stability of nitrosoisocyanate OCN–NO and nitroisocyanate OCN–NO 2 were investigated using ab initio calculations. The calculations were carried out at DFT-B3LYP/6-311++G ∗∗ level. From the calculation nitrosoisocyanate was predicted to exist predominantly in the trans conformation with high trans– cis rotational barrier. The rotational barrier of the NO group was calculated to be about 6 kcal/mol, while that of the NO 2 group to be of about 2 kcal/mol. The vibrational frequencies were computed, normal coordinate calculations were carried out and potential energy distributions were calculated for both molecules. A complete vibrational assignment was provided for the normal modes of the two molecules.

Extremely high trans selectivity of Ti-MWW in epoxidation of alkenes with hydrogen peroxide

A novel titanosilicate with MWW topology, Ti-MWW, exhibits a behavior not observed on other titanosilicates such as TS-1, TS-2 and Ti-beta, in that it selectively epoxidizes trans isomers from a mixture of cis/trans alkenes with retention of stereochemistry.

日本の市販食品のトランス脂肪酸含量 ＶＩ チョコレート及びチョコレート菓子（原標題は英語）

Trans fatty acid content in domestic and imported chocolates and chocolate confectioneries were measured by gas-liquid chromatography and silver-ion thin-layer chromatography. Mean total trans fatty acid content in domestic chocolates (3.1%, 80 brands) exceeded that in imported products (1.3%, 10 countries, 37 brands). High trans fatty acid type hard butter was found to be used as a cocoa butter substitute several brands of domestic products but not in imported products. In chocolate cake, mean total trans fatty acid content was 7.3% for domestic (43 brands), and 3.2% for imported products (9 countries, 22 brands), these values exceeding those of chocolates. In domestic chocolate-applicated sweets, mean total trans fatty acid content in foreign-style confectioneries (29 brands), ice cream (25 brands), and spreads (5 brands) was 11.0%, 3.5%, and 14.1%, respectively. In imported chocolate-applicated sweets, baked confectioneries (7 countries, 10 brands) contained 8.7% trans fatty acid.

No Effect of Dietary Trans Isomers of α-linolenic Acid on Platelet Aggregation and Haemostatic Factors in European Healthy Men : The TRANSLinE Study

The aim of this study was to investigate the effect of trans α-linolenic acid on platelet aggregation and blood haemostasis. A randomized, double blind dietary intervention trial was carried out with healthy male volunteers (n=88) in three European centers. After a 6-week washout period where subjects avoided foods containing all trans fats, subjects either continued for 6 weeks with a low trans diet or a diet where trans α-linolenic acid provided 0.6% of energy (supplied as oil, margarine, cheese, muffins, and biscuits). At the end of the washout period the intake of trans polyunsaturated fats was 58±115 mg/day; this increased in patients on the high trans diet by +1344±328 mg/day, compared with +10±67 mg/day in patients on the low trans diet (p<0.01). The change in trans α-linolenic acid in plasma cholesteryl esters was 0.26±0.20 on the high trans and 0.00±0.07% of fatty acids on the low trans diet (p<0.001). No effect of the high trans diet was observed on platelet aggregation: collagen EC 50 high trans 157±100, low trans 152±90 ng/mL (NS); U44619 EC 50 high trans 81±61, low trans 59±27 nM (NS). The high trans diet did not affect platelet thromboxane production, fibrinogen levels, factor VII, activated factor VIIa, or plasminogen activator inhibitor activity. There were no center-specific differences in response to the high trans diet. A relatively high amount of trans α-linolenic acid for 6 weeks does not increase the risk of coronary heart disease by promoting platelet aggregation and blood coagulation.

Diastereoselective synthesis of 2,5-disubstituted tetrahydrofuran derivatives

5-Substituted lactol 1 was converted to 2,5-disubstituted tetrahydrofuran derivatives by a Lewis acid-promoted reaction with allylsilanes. High trans selectivity (12:1) was obtained when hindered allylsilane 8 was employed. 5-Substituted lactol 16 was transformed into 2,5- cis-disubstituted tetrahydrofuran 17b (6:1 ratio) by a TiCl 4-promoted intramolecular allyl transfer process. Additionally, 2,5- cis-disubstituted tetrahydrofuran derivatives were obtained in good yields and diastereoselectivities after alkyllithium addition to lactone 6, followed by Et 3SiH/BF 3·OEt 2 reduction of the corresponding hemiketals.