Jan Bergman

Synthesis of the marine alkaloid leucettamine B

Abstract The marine natural product leucettamine B 2 has been prepared in good yield via two different routes, starting with glycine or with 3-methyl thiohydantoin, involving simple aldol condensation, and finally transamination of the thiohydantoin derivative.

STEREOSPECIFIC SYNTHESIS AND CRYSTAL STRUCTURE OF THE RACEMATE OF 1-THIA-2-TELLURA-1(1-ALLYL-4-CHLORO)CYCLOPENTANE 2,2,2-TRICHLORIDE

Abstract Tellurium tetrachloride and diallyl sulfide react to stereospecifically formed crystals of 1-thia-2-tellura-1(1-allyl-4-chloro)cyclopentane 2,2,2-trichloride. According to single-crystal X-ray determination the structure consists of the (R,R)-(S,S) racemate unit with a centre of symmetry. In the asymmetric units the TeIV-atoms display distorted ψ octahedral coordination. Although the equatorial Te-S bond length is 2.763(1) A, the Natural Bond Order (NBO) analysis reveals significant electronic interaction.

Stereoselective synthesis, molecular structure and NBO analyses of cis-3,5-di(chloromethyl)-1,4-oxatellurane(IV) 4,4-dichloride

Abstract Tellurium tetrachloride and diallyl ether give stereoselectively cis-3,5-di(chloromethyl)-1,4-oxatellurane(IV) 4,4-dichloride. The structure was determined by single crystal X-ray diffraction. The coordination around the TeIV ion is a distorted Φ trigonal bipyramid with two chlorine atoms in the axial positions. Two of the equatorial sites are occupied by carbon atoms, with the lone electron pair located at the third position. The six-membered heterocycle displays a chair conformation. The crystal structure consists of ribbons with Te·Cl contaacts. The NBO (Natural Bond Order) analyses carried out by both HF/STO-3G∗ and HF/LANL1DZ level of theory gave different results. No intermolecular interaction (>1 kcal mol−1) was found by HF/STO3G∗, whereas the main interaction can be seen between a lone pair of Cl(2) and the antibonding orbital between Te(1) and C(1) by RHF/LANL1DZ (1.1 kcal mol−1).

Comments on the Asymmetric Synthesis ofChrysogine

The absolute configuration of the mould metabolite chrysogine, (S)-(-)-2-(1-hydroxyethyl)quinazolin-4(3H )-one, was first determined by asymmetric synthesis in 1990 and not in 1996 as recently claimed.