New NOAH modules for structure elucidation at natural isotopic abundance

Structure Elucidation of a New

In the course of our continuing search for novel antimicrobial agents,1-4) we have isolated a novel diketopiperazine, Sch 725418 (1), from culture Micromonospora sp. In this paper, we describe the isolation and structure elucidation of 1 using high resolution ESI-MS and extensive NMR spectroscopic analysis. Fermentation studies of the SP culture 94-00889 were carried out in shake flasks. Stock ...

Novel Estimation Methods for Unsupervised Discovery of Latent Structure in Natural Language Text by Noah Ashton

This thesis is about estimating probabilistic models to uncover useful hidden structure in data; specifically, we address the problem of discovering syntactic structure in natural language text. We present three new parameter estimation techniques that generalize the standard approach, maximum likelihood estimation, in different ways. Contrastive estimationmaximizes the conditional probability ...

¹³C NMR metabolomics: applications at natural abundance.

(13)C NMR has many advantages for a metabolomics study, including a large spectral dispersion, narrow singlets at natural abundance, and a direct measure of the backbone structures of metabolites. However, it has not had widespread use because of its relatively low sensitivity compounded by low natural abundance. Here we demonstrate the utility of high-quality (13)C NMR spectra obtained using a...

13C NMR Metabolomics: Applications at Natural Abundance

Some Recent Aspects in the Structure Elucidation of Natural Products

Although in the past 20 yr a large number of new synthetic approaches have been developed methods of isolation and structural elucidation have changed more dramatically in the last two decades than have those of synthesis. For the purification of natural products more and more different chromatographic techniques like paper, thin-layer, column, and gas—liquid chromatography are being used. Char...