Total Synthesis of Woodrosin I—Part 1: Preparation of the Building Blocks and Evaluation of the Glycosylation Strategy

Abstract

The preparation of three building blocks required for the total synthesis of woodrosin I (1) is outlined, a complex resin glycoside bearing a macrolide ring which spans four of the five sugars of its oligosaccharide backbone. Key steps involve the enantioselective, titanium-catalyzed addition of dipentylzinc to 5-hexenal, the glycosylation of the resulting alcohol 18 with the glucose-derived trichloroacetimidate 7, and further elaboration of the resulting product 19 into disaccharide 22 on treatment with the orthogonally protected glycosyl donor 15. The trichloroacetimidate method is also used for the formation of the second synthon represented by disaccharide 38. A model study shows that the assembly of the pentasaccharidic perimeter of 1 depends critically on the phasing of the glycosylation events between fragments 22, 38 and the rhamnosyl donor 27 due to the severe steric hindrance in the product. A particularly noteworthy finding is the fact that diol 22 can be regioselectively glycosylated at the 3'-OH group in high yield without protection of the neighboring 2'-OH function.

A Bacteroidetes locus dedicated to fungal 1,6-β-glucan degradation: Unique substrate conformation drives specificity of the key endo-1,6-β-glucanase

“…A mixture of 2- O -acetyl-3,4,6-tri- O -benzyl- d -glucopyranosyl trichloroacetimidate 3 (40) (20 mg, 0.027 mmol), acceptor 2 (13.0 mg, 0.021 mmol) and freshly activated 4 Å molecular sieves in dry toluene (1.5 ml) was stirred at −30 °C under N 2 for 1 h. TfOH in toluene (1% v/v, 8 μl, 0.0006 mmol) was then added, and the mixture allowed to warm to −10 °C and stirred for 30 min. The reaction was quenched with triethylamine (0.1 ml).…”

Crystal Structure of Tricolorin A: Molecular Rationale for the Biological Properties of Resin Glycosides Found in Some Mexican Herbal Remedies

“…[5,6] Fürstner and Müller later used a ring-closing-metathesis strategy to form the macrolactone moiety and succeeded in synthesizing tricolorin A [7] and several other resin glycosides. [8,9] Tricolorin A demonstrates several biological activities of therapeutic interest, such as mammalian cytotoxicity against cultured P-338 and human breast cancer cells, [2] antibacterial activity against Staphyloccocus aureus and Mycobacterium tuberculosis, [1] and antifungal potential correlated to its (1!3)b-d-glucan synthase inhibitory activity. [10] In the cover crop, tricolorin A acts as a nonprotonophoric uncoupler of photophosphorylation and inhibits electron transport in the photosystem II of chloroplasts.…”

Total Synthesis and Absolute Configuration of Epicoccamide D, a Naturally Occurring Mannosylated 3‐Acyltetramic Acid

“…This route gave distinctly higher yields of 6 than an alternative one starting from a glucosyl bromide [11] and also when compared with a longer glucal-based route. [12] The coupling of imidate 6 with the monoprotected diol 5, available in two steps from hexadecanolide (see the Supporting Information), required a good deal of experimentation for optimum results. Eventually, b-glucoside 10 was obtained in 84 % yield in the presence of borontrifluoride etherate (Scheme 3).…”