Non-cross-linked polystyrene-supported 2-imidazolidinone chiral auxiliary: synthesis and application in asymmetric alkylation reactions

• Quynh Pham Bao Nguyen and
• Taek Hyeon Kim

Beilstein J. Org. Chem. 2013, 9, 2113–2119, doi:10.3762/bjoc.9.248

• polystyrene (NCPS)-supported 2-phenylimino-2-oxazolidine, which facilitated the synthesis of several chiral amides in excellent stereoselectivity (>96% ee). However, the sterically undemanding methylation has not been investigated [20]. Recently, we introduced 2-imidazolidinone [26][27], a versatile auxiliary

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

• (oxazolidine, cyclic ketal, etc.), or deactivated by conversion into amide or carbamate functions. Due to these protective groups even metathesis catalysts sensitive to functionalities can act efficiently under reaction conditions where an adequate balance between activity/stability factors has been met. In

Asymmetric synthesis of tertiary thiols and thioethers

• Jonathan Clayden and
• Paul MacLellan

Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68

• and co-workers postulated that poor reactivity and facial selectivity in conjugate additions with sulfur could be minimised by an intramolecular approach [47][48]. A Lewis acid-promoted sulfur migration within N-enoyl oxazolidine-2-thione substrates 56 followed by hydrolysis gave optically pure

• of enone 46. Organocatalytic conjugate addition to nitroalkenes 49. Preparation of β-amino acid 54. Sulfur migration within oxazolidine-2-thiones 56. Preparation of thiols 62 by self-regeneration of stereocentres. Synthesis of (5R)-thiolactomycin. Preparation of tertiary thiols and thioethers via α

Brønsted acid-promoted azide–olefin [3 + 2] cycloadditions for the preparation of contiguous aminopolyols: The importance of disiloxane ring size to a diastereoselective, bidirectional approach to zwittermicin A

• Hubert Muchalski,
• Ki Bum Hong and
• Jeffrey N. Johnston

Beilstein J. Org. Chem. 2010, 6, 1206–1210, doi:10.3762/bjoc.6.138

• pure (−)-zwittermicin A (1) is based on a short synthesis of the C9–C15 aminopolyol core that takes advantage of its underlying C2 symmetry, as outlined in Scheme 1. Desymmetrization and functionalization of the bis(oxazolidine dione) 2 provides us with a foundation for the synthesis of 1 and would

• and 14a could be converted to the corresponding bis(oxazolidine diones) by treatment with triflic acid at room temperature (Scheme 3). The silyl protecting groups were removed with HF·pyridine in THF, and 15 and 16 converted to the same 1,3-diol 17 (Scheme 3). Conclusion In summary, this first study

Asymmetric synthesis of biaryl atropisomers by dynamic resolution on condensation of biaryl aldehydes with (−)-ephedrine or a proline- derived diamine

• Ann Bracegirdle,
• Jonathan Clayden and
• Lai Wah Lai

Beilstein J. Org. Chem. 2008, 4, No. 47, doi:10.3762/bjoc.4.47

• % yield. Hydrolysis and reduction of the major diastereoisomeric product of the reaction yields atropisomeric biaryls in >99:1 enantiomeric ratios. Keywords: atropisomer; biaryl; dynamic resolution; ephedrine; imdazolidine; oxazolidine; Introduction Atropisomeric biaryl compounds have proved to be among

• corresponding oxazolidine. (2S,4S,5R)-2-(6,2′-Dimethoxybiphenyl-2-yl)-3,4-dimethyl-5-phenyloxazolidine (10a) Aldehyde 6a (608 mg, 2.51 mmol) gave, after flash chromatography on alumina (eluent 5:1 v/v petroleum ether/EtOAc), the title compound 10a as a white solid (731 mg, 75%). Mp 131–135 °C; 1H NMR spectra