An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• between glyoxilic acid monohydrate (3.13) and 1,4-dithiane-2,5-diol (3.14) (Scheme 33) [87]. Subsequent acetylation of the hydroxy group followed by ester formation using (−)-L-menthol permits crystallisation separation of the two diastereoisomers. The use of bis-TBDMS-cytosine as a coupling partner in

A reductive coupling strategy towards ripostatin A

• Kristin D. Schleicher and
• Timothy F. Jamison

Beilstein J. Org. Chem. 2013, 9, 1533–1550, doi:10.3762/bjoc.9.175

• corresponding diester. Preliminary investigation indicates that oxidation of the diol derived from 6 is complicated by the 1,5-relationship of the alcohols. Despite the greater complexity inherent to this alternative, differentiation of the alcohols allowing for sequential oxidation may be necessary. Dithiane

• just 30 minutes; a significant improvement over heating the reaction mixture in toluene under reflux, which typically required 48 hours to obtain a comparable yield. Reduction and oxidation afforded the aldehyde 47, which could then be converted to dithiane 41. Unfortunately, attempts to couple 41 with

• an oxygenated epoxide fragment under a variety of conditions reported by Smith for lithiation and electrophilic trapping [51] were unsuccessful. We suspected that the lithiated dithiane was not being generated and decided to investigate this step of the reaction independently of reaction with the

Re₂O₇-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles

• Wantanee Sittiwong,
• Michael W. Richardson,
• Charles E. Schiaffo,
• Thomas J. Fisher and
• Patrick H. Dussault

Beilstein J. Org. Chem. 2013, 9, 1526–1532, doi:10.3762/bjoc.9.174

• furnish a dithioacetal or a 1,3-dithiane. A ketone substrate did not react under these conditions (not shown). The mono- and dithioacetalization reactions were visibly different from the O-acetalizations described above. Whereas addition of Re2O7 to a hemiacetal in the presence of an alcohol generates a

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• of this device was for the preparation of a series of hydrazones. A continuous aqueous extraction to remove the excess hydrazine enabled the product to be collected in high purity (Figure 29). Other applications reported in this work include alkene epoxidation and dithiane preparation. Dispersion of

Alternaric acid: formal synthesis and related studies

• Michael C. Slade and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2013, 9, 166–172, doi:10.3762/bjoc.9.19

• insufficient for adequate stereocontrol in the three-component coupling reaction [34]. An additional branch point in the carbon backbone, such as in 16b, was deemed necessary. The 1,3-dithiane group in aldehyde 16ba was conceived as a promising candidate for a stereocontrolling element due to its large size

• glyoxylate 1a under previously optimized conditions, high efficiency was achieved along with excellent (>20:1) stereochemical control for the formation of three-component-coupling product 17 (Scheme 7) [41][42][43][44]. To verify that the dithiane was acting in the desired fashion, and to rule out chelation

• from one of the Lewis basic sulfur atoms, derivatization to a lactone was carried out. The dithiane was cleaved to the ketone 18, which underwent a 1,3-syn-selective reduction [45]. The resultant diol 19 was subjected to acidic conditions to effect cleavage of the tert-butyl ester and lactonization to

Multivalent display of the antimicrobial peptides BP100 and BP143

• Imma Güell,
• Rafael Ferre,
• Kasper K. Sørensen,
• Esther Badosa,
• Iteng Ng-Choi,
• Emilio Montesinos,
• Eduard Bardají,
• Lidia Feliu,
• Knud J. Jensen and
• Marta Planas

Beilstein J. Org. Chem. 2012, 8, 2106–2117, doi:10.3762/bjoc.8.237

• functionalized cyclo-dithioerythritol (cDTE) and α-D-galactopyranoside (Galp) templates have been described in earlier publications [23][30]. Synthesis of carbopeptide (KKLFKKILKYL-C2H4N)2-cDTE (1) (4R,5S)-1,2-Dithiane-4,5-diyl bis(Boc)2-Aoa (cDTE) (12.7 mg, 18.2 μmol) was dissolved in TFA/CH2Cl2 (1:1, 2 mL) and

• stirred for 1 h. The solution was then concentrated in vacuo, redissolved in a small amount of water and lyophilized to afford (4R,5S)-1,2-dithiane-4,5-diyl bis(2-Aoa) as a white powder. This template and the peptide aldehyde 4 (65.7 mg, 45.0 μmol) were dissolved in 6.2 mL of a 1:1 solution of CH3CN and

• +, 532.2 [M + 6H]6+; HRMS–MALDI (m/z): [M + Na]+ calcd for C156H264N36NaO30S2, 3208.9753; found, 3208.9737. Synthesis of carbopeptide (KKLfKKILKYL-C2H4N)2-cDTE (2) (4R,5S)-1,2-Dithiane-4,5-diyl bis(2-(Boc)2-Aoa) (cDTE) (4.8 mg, 6.9 μmol) was dissolved in TFA/CH2Cl2 (1:1, 1 mL) and stirred for 1 h. The

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• steps via the Fleet protocol [55]. The tandem RCM/dihydroxylation sequence was also applied by Davis et al. in the synthesis of (−)-2,3-trans-3,4-cis-dihydroxyproline. In this case, an α-amino aldehyde, prepared by addition of a 1,3-dithiane to a chiral N-sulfinyl imine, was used as the chiral starting

Synthesis of (3R,5R)-harzialactone A and its (3R,5S)-isomer

• Gowravaram Sabitha,
• Rangavajjula Srinivas,
• Sukant K. Das and
• Jhillu S. Yadav

Beilstein J. Org. Chem. 2010, 6, No. 8, doi:10.3762/bjoc.6.8

• . Epoxide opening with thioacetal and diastereoselective reductions are used as key reactions. Keywords: dithiane; harzialactone A; hydroxyl directed reduction; stereoisomer; Introduction Marine microorganisms such as bacteria, fungi, and microalgae have proved to be a rich source of structurally novel

• successive protecting group transformations. 3 can be made by hydroxyl directed reduction of 4 which in turn could be prepared by epoxide 6 opening with dithiane 5. Results and Discussion The synthesis of natural (3R,5R)-1 was initiated from the known epoxide 6, which is commercially available. Treatment of

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• the molecule. The synthesis followed Scheme 45 with a noteworthy methoxy-ketal formation going through the dithiane 161. The introduction of the aziridine was elaborated via a diol in the usual way [119]. However, three equivalents of osmium tetroxide and one week of reaction time were needed to get