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Nicolai Cramer

Publications associées (116)

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Preparation of UDP-galacturonic acid using UDP-sugar pyrophosphorylase

Nicolai Cramer

UDP-galacturonic acid, the activated form of galacturonic acid (GalUA), is synthesized both de novo and by salvage pathways. The UDP-GalUA pyrophosphorylase gene involved in the salvage pathway has not been identified. Here we show that UDP-sugar pyrophosp ...

Elsevier2006

Total synthesis and NMR investigations of cylindramide

Nicolai Cramer

Cylindramide (I) was built up from three components: a hydroxyornithine deriv. II, a tetrazolylsulfone III, and a substituted pentalene subunit IV. Deriv. II was prepd. in a six-step reaction sequence involving the Wittig reaction and a Sharpless asym. dih ...

Wiley-VCH Verlag GmbH & Co. KGaA2006

Enantioselective total synthesis of cylindramide

Nicolai Cramer

Key steps in the convergent enantioselective synthesis of the cytotoxic natural product cylindramide are tandem Michael addn./electrophilic trapping reactions, Sonogashira coupling, Julia-Kocienski olefination, and macrocyclization. For example, the Sonoga ...

Wiley-VCH Verlag GmbH & Co. KGaA2005

Acid-promoted retro-Mannich reaction of N-protected tropenones to 2-substituted pyrroles

Nicolai Cramer

N-protected tropenone undergoes highly regioselective retro-Mannich reactions to 2-pyrrolyl ketones in the presence of Lewis or Bronsted acids. Analogously, a pyrrole deriv. was obtained by using subsequent nucleophilic trapping with trimethylsilanecarboni ...

Wiley-VCH Verlag GmbH & Co. KGaA2004

Enantioselective desymmetrization of tropinone derivatives by hydroboration

Nicolai Cramer

N-Protected tropenone derivs. I (R = CO2Me, CBZ, Ts) prepd. from the resp. pyrroles and tetrabromoacetone, were used as starting materials for desymmetrization by hydroboration of the C-C double bond. Hydroboration of I with (-)-(Ipc)2BH followed by oxidn. ...

Georg Thieme Verlag2003

Enzymatic resolution of tropinone derivatives

Nicolai Cramer

The lipase-mediated kinetic resoln. of racemic scopoline and 6-hydroxytropinone is reported. Whereas (¬±)-scopoline is difficult to resolve due to steric hindrance of the hydroxy function, the resoln. of (¬±)-6-hydroxytropinone with vinyl acetate as acyl d ...

Georg Thieme Verlag2003