Physiatry Practice Management Resources

Abstract

Treatment of 5-(tert-butyldimethylsilyl)-2,3-O-isopropyllidene-D-ribose with lithium acetylides gave a mixtures of syn- and anti-alkynols 2a-2c which were separated following protection as methoxymethyl ethers. These were converted to the corresponding iodides which underwent 6-exo-dig radical cyclisation to afford chiral cyclohexanes and carabsugars. Oxidation of the primary alcohols 6a-b gave the corresponding aldehydes which on treatment with Grignard reagents afforded a mixture of alcohols. The corresponding iodides underwent similar 6-exo-dig cyclisation to give fully functionalised cyclohexanes.

Beilstein J. Org. Chem.2008, 4, No. 43.  doi:10.3762/bjoc.4.43

Abstract

A convenient and practical synthesis of imidazol-1-yl-acetic acid hydrochloride was achieved via N-alkylation of imidazole using tert-butyl chloroacetate followed by a non-aqueous ester cleavage of the resulting imidazol-1-yl-acetic acid tert-butyl ester in the presence of titanium tetrachloride. The synthesized imidazol-1-yl-acetic acid hydrochloride was then utilized to prepare zoledronic acid.

Beilstein J. Org. Chem.2008, 4, No. 42.  doi:10.3762/bjoc.4.42

Abstract

The first synthesis of 2,3,6,7-tetrabromoanthracene is presented, starting from benzene in a straightforward four step synthesis.

Beilstein J. Org. Chem.2008, 4, No. 41.  doi:10.3762/bjoc.4.41

Abstract

The coupling of arylboroxines with a variety of amines, amides, imides and sulfonamides catalyzed by a copper salt/EtOH system has been developed. In the absence of a base or additive the corresponding N-arylation products were obtained in moderate to excellent yields.

Beilstein J. Org. Chem.2008, 4, No. 40.  doi:10.3762/bjoc.4.40

Abstract

Melanotan II is a synthetic cyclic heptapeptide used to prevent a sunlight-induced skin cancer by stimulating the skin tanning process. In this paper we report the first solution phase synthesis of the title compound. The hexapeptide sequence has been assembled by [(2+2)+1+1] scheme. After removing the orthogonal protection, a carbodiimide mediated lactamization, involving the ε-amino group of lysine and γ-carboxy group of aspartic acid, led to a cyclic intermediate. Appending N-acetylnorleucine concluded the assembly of melanotan II molecule. Protection of the lateral groups in arginine and tryptophan was omitted for atom and step economy reasons. The total synthesis of melanotan II was accomplished in 12 steps with 2.6% overall yield, affording >90% pure peptide without using preparative chromatography.

Beilstein J. Org. Chem.2008, 4, No. 39.  doi:10.3762/bjoc.4.39

Abstract

Tandem deoxygenation–neophyl-type radical rearrangement–electrophile trapping using xanthates from 7-azabenzonorbornadienes gives 3-exo-substituted 2-aza-5,6-benzonorbornenes, which in some cases undergo isomerisation to (aminomethyl)indenes. The starting xanthates are accessible in good yields and high enantiomeric ratios via asymmetric hydroboration of (aryne/pyrrole-derived) 7-azabenzonorbornadienes. Oxidation (using RuO₄) and Birch reduction of the 2-aza-5,6-benzonorbornenes provide access to substituted pyrrolidines and tetrahydroindenes, respectively.

Beilstein J. Org. Chem.2008, 4, No. 38.  doi:10.3762/bjoc.4.38

Abstract

Background

The chemistry of tetralin-1,4-dione, the stable tautomer of 1,4-dihydroxynaphthalene, has not been explored previously. It is readily accessible and offers interesting opportunities for synthesis.

Results

The title reactions were explored. L-Selectride reduced the diketone to give preferentially the cis-diol (d.r. 84 : 16). Red-Al gave preferentially the trans-diol (d.r. 13 : 87). NaBH₄, LiAlH₄, and BH₃ gave lower diastereoselectivities (yields: 76–98%). Fractional crystallization allowed isolation of the cis-diol and the trans-diol (55% and 66% yield, respectively). Borane was used to cleanly give the mono-reduction product. Highly enantioselective CBS reductions afforded the trans-diol (72% yield, 99% ee) and the mono-reduction product (81%, 95% ee).

Conclusion

Diastereoselective and enantioselective reductions of the unexplored tetralin-1,4-dione provides a very convenient entry into a number of synthetically highly attractive 1,4-tetralindiols and 4-hydroxy-1-tetralone.

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

Abstract

Several lower-rim perfluoroalkylated (fluorous) calix[4]arenes have been synthesized by O-alkylation of the parent calix[4]arene. The compounds are formed in the cone conformation. They are soluble in several fluorous solvents and show promise for use in sensing, selective extractions and other applications.

Beilstein J. Org. Chem.2008, 4, No. 36.  doi:10.3762/bjoc.4.36

Abstract

A mild synthetic method for N-formyl-Met-Leu-Phe-OH (1) is described. After Fmoc solid phase peptide synthesis, on-bead formylation and HPLC purification, more than 30 mg of the fully ¹³C/¹⁵N-labelled tripeptide 1 could be isolated in a typical batch. This peptide can be easily crystallised and is therefore well suited as a standard sample for setting up solid-state NMR experiments.

Beilstein J. Org. Chem.2008, 4, No. 35.  doi:10.3762/bjoc.4.35

Abstract

End game synthetic strategy studies towards the total synthesis of the vibsanin type diterpenes, vibsanin E, 3-hydroxyvibsanin E, furanovibsanin A, and 3-O-methylfuranovibsanin A are discussed, with focus on construction of the side chain and peripheral functionality associated with this group of natural products is the current focus of this report.

Beilstein J. Org. Chem.2008, 4, No. 34.  doi:10.3762/bjoc.4.34