General Approach to Anthrapyran Antibiotics Exemplified by the Synthesis of rac‐γ‐Indomycinone

Abstract

A new general route to the anthrapyran antibiotics is presented, which allows the attachment of various branched side chains. A key step is the Baker-Venkataraman rearrangement of the propionate 9 to the diketone 10. Acidcatalyzed cyclization gives the ethyl-branched anthrapyranone 11, serving as the starting material for further sidechain elongation. For example, the ethyl-substituted anthra-

Studies toward the syntheses of pluramycin natural products. The first total synthesis of isokidamycin

“…13c-e, 26 Althoughtreating 52 with avariety of Brønsted acids led largely to recovered starting material under most of the conditions examined, we discovered that heating 52 in aqueous acetonitrile containing LiBF 4 gave the benzofuranone 53 in 80% yield (Scheme 11); the undesired 5- exo -digonal cyclization completely dominated in complete preference to the desired 6- endo -digonal cyclization mode. The cyclizations of phenolic ynones to give benzofuranones was known, 26 and in some cases may be avoided by first converting the ynone to a vinylogous amide.…”

“…The potential of kidamycin ( 1 ) to serve as an anticancer agent, coupled with its challenging structure have led to a number of synthetic investigations, but no member of the pluramycin family has been synthesized via these approaches. 12,13 …”

The synthesis and biological activity of novel anthracenone-pyranones and anthracenone-furans

“…Coupled with the Augustine olefination procedure by Krohn et al, this sequence could provide a range of substituted 4-pyranone derivatives. 10,30 We next examined this first group of compounds (4, 8 and 12, 14 and 16) for in vitro cell growth inhibition against a panel of nine human cancer cell lines including: HT29 (colorectal carcinoma); MCF-7 (breast adenocarcinoma); A2780 (ovarian carcinoma); H460 (lung carcinoma); A431 (epidermoid carcinoma); DU145 (prostate carcinoma); BE2-C (neuroblastoma); SJG2 (glioblastoma); MIA (pancreatic carcinoma) and SMA (glioblastoma). As in previous investigations, 31 16 Scheme 2.…”

Total Synthesis of γ-Indomycinone and Kidamycinone by Means of Two Regioselective Diels–Alder Reactions

“…Following a biomimetic strategy, Mc Donald published in 2005 an interesting synthesis giving access to both kidamycin and altromycin aglycones from a common tetracyclic intermediate . The same biomimetic approach was applied in 2007 to build the backbone of γ-indomycinone which was also synthesized by several groups through Diels–Alder reactions. − Construction of aglycones is therefore well-known but, to the best of our knowledge, despite many endeavors, interest and developments during the past decade, − there is still no reported methodology to prepare natural pluramycin containing both β-angolosamine (see Figure , ring E) and α- N , N -dimethylvancosamine (see Figure , ring F) moieties. Two major problems can be highlighted: (1) the introduction of the glycosidic subunits at the first stages of a linear synthesis increases possible unwanted side reactions, such as epimerization, (2) the introduction of the glycosidic subunits by direct glycosylation reactions in the last steps of the synthesis, on a properly functionalized and bulky tetracycle, may suffer from poor regio- and/or stereoselectivity in combination with poor yields.…”