Diastereoselective and enantioselective reduction of tetralin- 1,4-dione

• E. Peter Kündig and
• Alvaro Enriquez-Garcia

Beilstein J. Org. Chem. 2008, 4, No. 37, doi:10.3762/bjoc.4.37

• is important to mention here that these reactions do not occur when tautomer 1 is used. The reductions with NaBH4 (Table 1, entry 1) and BH3·THF (entry 4) gave the diols in high yields but with low diastereoselectivity, slightly favoring the cis-diastereoisomer 6. In contrast, reduction with LiAlH4

• but recrystallization from iPr2O gave cis-1,4-dihydroxytetralin (6) in 66% yield. Diols 6 and 7 have been reported previously. They were obtained by treatment of tetralin with NBS to give a 1 : 1 mixture of the corresponding cis and trans-dibromides, which were converted into diacetates with AgOAc (81

• access to this C2 symmetric chiral diol. Compound (−)-(1R,4R)-7 was previously obtained by HPLC separation of a 1 : 1 mixture of the cis- and trans-diols obtained in 55% yield from a four step sequence from (R)-1-tetralol [12]. Mono-reduction of 2 Mono-reduction was achieved with a reduced amount of

Control of asymmetric biaryl conformations with terpenol moieties: Syntheses, structures and energetics of new enantiopure C₂-symmetric diols

• Y. Alpagut,
• B. Goldfuss and
• J.-M. Neudörfl

Beilstein J. Org. Chem. 2008, 4, No. 25, doi:10.3762/bjoc.4.25

• Y. Alpagut B. Goldfuss J.-M. Neudorfl Institut für Organische Chemie, Universität zu Köln, Greinstrasse 4, D-50939 Köln, Germany. Fax: +49(0)221-470-5057, http://www.uni-koeln.de/goldfuss. 10.3762/bjoc.4.25 Abstract New enantiopure, C2-symmetric biphenyl-2,2′-diols based on (−)-menthone (BIMOL

• ), (−)-verbenone (BIVOL) and (−)-carvone (BICOL and hydrogenated BIMEOL), are accessible via short, synthetic routes. All diols form intramolecular hydrogen bonds and hence can be employed as chelating ligands for catalyst design, as it demonstrated for the (−)-fenchone based BIFOL. The sense of asymmetry of the

• ONIOM evaluations of the diols and their diastereomeric conformers. The experimentally observed biphenyl conformations are all energetically preferred, i.e. with 1.3 kcal/mol for (M)-BIMOL, with 5.1 kcal/mol for (P)-BIVOL, with 5.8 kcal/mol for (P)-BICOL, and with 5.4 kcal/mol for (P)-BIMEOL. Keywords

Solvent- controlled regioselective protection of allyl- 4,6-benzylidene glucopyranosides

• Kerry Ann Ness and
• Marie E. Migaud

Beilstein J. Org. Chem. 2007, 3, No. 26, doi:10.1186/1860-5397-3-26

• functional group manipulations required to access suitable synthetic precursors. For hexopyranoses, acylation of cis-diols can be achieved with high regioselectivity either by means of metal activators such as tin [1][2][3], silver [4], boron [5] or copper [6] or by exploiting the relative reactivity of

• hydroxyl groups [7][8]. However, metal-promoted alkylation and base-catalysed acylation of diols have proven to be highly undependable in the case of glucose and other cyclic trans-diols, where both hydroxyl groups are equatorial. For instance, reports of identical procedures describing the tin-catalysed

The vicinal difluoro motif: The synthesis and conformation of erythro- and threo- diastereoisomers of 1,2-difluorodiphenylethanes, 2,3-difluorosuccinic acids and their derivatives

• David O'Hagan,
• Henry S. Rzepa,
• Martin Schüler and
• Alexandra M. Z. Slawin

Beilstein J. Org. Chem. 2006, 2, No. 19, doi:10.1186/1860-5397-2-19

• conversion of vicinal diols to vicinal difluorides has been explored with some success. For example both erythro and threo stereoisomers of dimethyl 2,3-difluorosuccinic acid were obtained either from methyl esters of the L-tartrate 1 or the meso-tartrate 1 by treatment with SF4/HF (Scheme 1) [6][7

• replace SF4 with DAST failed in trying to develop an analogous small scale laboratory process. Deoxofluor is finding use in the stereoselective conversion of vicinal diols to vicinal difluorocompounds and seems less prone to elimination than DAST [8]. In addition, Deoxofluor has been reported to be

The oxanorbornene approach to 3-hydroxy, 3,4-dihydroxy and 3,4,5-trihydroxy derivatives of 2-aminocyclohexanecarboxylic acid

• Ishmael B. Masesane,
• Andrei S. Batsanov,
• Judith A. K. Howard,
• Raju Mondal and
• Patrick G. Steel

Beilstein J. Org. Chem. 2006, 2, No. 9, doi:10.1186/1860-5397-2-9

• afforded the trans β-amino acid derivative 22 as established by NMR experiments. Having prepared the 4,5-cis diol, we turned our attention to the synthesis of the corresponding trans diols. These could be prepared by simple hydrolytic cleavage of epoxides 10–13. In line with this plan, treatment of 12 with

• ring protons (H-1, H-2, H-3, H-4 and H-5) is consistent with anti diaxial relationships. Such assignments are supported by nOe interactions between H-1 and H-3, H-1 and H-5 and also H-2 and H-4, Figure 3. Similar treatment of epoxides 11 and 13 then afforded the corresponding anti 4,5 diols. Subsequent

Synthesis and glycosidase inhibitory activity of new hexa- substituted C8-glycomimetics

• Olivia Andriuzzi,
• Christine Gravier-Pelletier,
• Gildas Bertho,
• Thierry Prangé and
• Yves Le Merrer

Beilstein J. Org. Chem. 2005, 1, No. 12, doi:10.1186/1860-5397-1-12

• acid catalyst such as ytterbium triflate, revealed unsuccessful, only leading to recover the starting material. To overcome this difficulty, we turned to a more electrophilic sulfate moiety [36] (Scheme 3). Thus, treatment of the cis-diols 3 and 4 with thionyl chloride in the presence of triethylamine

Synthesis of 2,6-trans- disubstituted 5,6-dihydropyrans from (Z)-1,5-syn-endiols

• Eric M. Flamme and
• William R. Roush

Beilstein J. Org. Chem. 2005, 1, No. 7, doi:10.1186/1860-5397-1-7

• /1860-5397-1-7 Abstract Certain (Z)-1,5-syn-diols 2 may be converted into 2,6-trans-5,6-dihydropyrans by using phosphonium salt 4 or phosphorane 5 as dehydrating agents. A more general four step procedure converts the (Z)-1,5-syn-endiols into enantiomeric dihydropyrans ent-3 via regioselective

• enantioselectivity.[1] In connection with an ongoing natural product synthesis project, we were interested in developing methods to transform diols 2 into dihydropyrans 3 or the enantiomeric dihydropyrans ent-3 through complementary, regioselective cyclodehydration processes (Scheme 1). 2,6-Disubstituted

• ) ring closing metathesis,[12][13] (iv) vinylsilane cyclization of oxocarbenium ions,[14] and (v) intramolecular allylations.[15][16] However, we were unaware of any reports that describe the direct conversion of 1,5-diols containing an internal olefin such as 2 directly to 2,6-trans-disubstituted 5,6