Covering: 1997 to 2010. The angucycline group is the largest group of type II PKS-engineered natural products, rich in biological activities and chemical scaffolds. This stimulated synthetic creativity and biosynthetic inquisitiveness. The synthetic studies used five different strategies, involving Diels-Alder reactions, nucleophilic additions, electrophilic additions, transition-metal mediated cross-couplings and intramolecular cyclizations to generate the angucycline frames. Biosynthetic studies were particularly intriguing when unusual framework rearrangements by post-PKS tailoring oxidoreductases occurred, or when unusual glycosylation reactions were involved in decorating the benz[a]anthracene-derived cores. This review follows our previous reviews, which were published in 1992 and 1997, and covers new angucycline group antibiotics published between 1997 and 2010. However, in contrast to the previous reviews, the main focus of this article is on new synthetic approaches and biosynthetic investigations, most of which were published between 1997 and 2010, but go beyond, e.g. for some biosyntheses all the way back to the 1980s, to provide the necessary context of information.

Scheme 10. Schmalz Synthesis of 3-Substituted Phthalides from 2-Formylketones Scheme 11. Enantioselective Synthesis of Phthalides via Ketone Hydroacylation Scheme 12. Synthesis of 3-Alkylphthalides from Sulfonylmethyl Benzoic Acids Scheme 13. Synthesis of an Isobenzofuranone via Thermolysis of a Bromomethylbenzoate Scheme 14. Kraus Approach to 3-Cyanophthalide Scheme 15. Ohzeki and Mori Synthesis of (−)-3-Butyl-7hydroxyphthalide Scheme 16. Asymmetric Dihydroxylation-Lactonization Route to Phthalides Chemical Reviews Review dx.

GilOII has been unambiguously identified as the key enzyme performing the crucial C-C bond cleavage reaction responsible for the unique rearrangement of a benz[a]anthracene skeleton to the benzo[d]naphthopyranone backbone typical for the gilvocarcin type natural anticancer antibiotics. Further investigations of this enzyme led to the isolation of a hydroxy-oxepinone intermediate which allowed important conclusions regarding the cleavage mechanism.

The lipopeptidyl nucleoside antibiotics reperesented by A-90289, caprazamycin, and muraymycin, are structurally highlighted by a nucleoside core that contains a nonproteinogenic β-hydroxy-α-amino acid named 5′-C-glycyluridine (GlyU). Bioinformatic analysis of the biosynthetic gene clusters revealed a shared open reading frame encoding a protein with sequence similarity to serine hydroxymethyltransferases, resulting in the proposal that this shared enzyme catalyzes an aldol-type condensation with glycine and uridine-5′-aldehyde to furnish GlyU. Using LipK involved in A-90289 biosynthesis as a model, we now functionally assign and characterize the enzyme responsible for the C-C bond-forming event during GlyU biosynthesis as an l-threonine:uridine-5′-aldehyde transaldolase. Biochemical analysis revealed this transformation is dependent upon pyridoxal-5′-phosphate, the enzyme has no activity with alternative amino acids such as glycine or serine as aldol donors, and acetaldehyde is a co-product. Structural characterization of the enzyme product is consistent with stereochemical assignment as the threo diastereomer (5′S,6′S)-GlyU. Thus this enzyme orchestrates C-C bond breaking and formation with concomitant installation of two stereocenters to make a new l-α-amino acid with a nucleoside side chain.

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After completing his B.Sc. (Hons) (1999, first class) and M.Sc. (2001, first class) degrees from the Vidyasagar University, he joined the group of Professor D. Mal at the

Several peptidyl nucleoside antibiotics that inhibit bacterial translocase I involved in peptidoglycan cell wall biosynthesis contain an aminoribosyl moiety, an unusual sugar appendage in natural products. We present here the delineation of the biosynthetic pathway for this moiety upon in vitro characterization of four enzymes (LipM-P) that are functionally assigned as (i) LipO, a l-methionine:uridine-5’-aldehyde aminotransferase, (ii) LipP, a 5’-amino-5’-deoxyuridine phosphorylase, (iii) LipM, a UTP:5-amino-5-deoxy-α-d-ribose-1-phosphate uridylyltransferase, and (iv) LipN, a 5-amino-5-deoxyribosyltransferase. The cumulative results reveal a unique ribosylation pathway that is highlighted by, among other features, uridine-5’-monophosphate as the source of the sugar, a phosphorylase strategy to generate a sugar-1-phosphate, and a primary amine-requiring nucleotidylyltransferase that generates the NDP-sugar donor.

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