Total Synthesis of Mycalisine B

Abstract

The first total synthesis of the marine nucleoside Mycalisine B—a naturally occurring and structurally distinct 4,5-unsaturated 7-deazapurine nucleoside—has been accomplished in 10 linear steps with 27.5% overall yield from commercially available 1,2,3,5-tetra-O-acetyl-ribose and tetracyanoethylene. Key steps of the approach include: (1) I2 catalyzed acetonide formation from 1,2,3,5-tetra-O-acetylribose and acetone at large scale; (2) Vorbrüggen glycosylation using N4-benzoyl-5-cyano-6-bromo-7H-pyrrolo[2,3–d]pyrimidine as a nucleobase to avoid formation of N-3 isomer; (3) mild and scalable reaction conditions.

Analysis of the Demonstration of the Target Cost of Aviation Equipment Repair Under the New Bargaining Rules

“…After a number of trial repairs and repair costs stabilize, the military will organize the price review of these trial repairs, comprehensively consider the law of trial repair cost changes, determine the approved repair price, and compare it with the tentative repair price. Make up the corresponding repair costs [1]. This pricing method makes up for all the costs of the repair unit, but because the repair price is closely related to the trial repair cost, the repair unit is not motivated to control the cost during the trial repair stage, and it is likely to incur more or more costs during the trial repair stage.…”

Palladium-Catalyzed Cyanation of Nucleobases: Total Synthesis of Toyocamycin, Sangivamycin, and a Mycalisine A Precursor

“…We further extended the utility of the Pd 2 (dba) 3 /Xantphos catalytic system for the synthesis of toyocamycin (10), an important antibiotic analogue of adenosine. 12,29,30 Firstly, the Vorbrüggen glycosylation between sugar 8 and nucleobase 4 was carried out in a similar manner to the above, followed by amination and sugar deprotection, providing nucleoside 9 in 65% overall yield (two steps).…”

“…26,27 Having demonstrated the potential of the cyanation protocol for iodo nucleosides, we next turned our attention toward the synthesis of a naturally occurring bioactive marine nucleoside, namely mycalisine A. 5,10 The reaction sequence began with a Vorbrüggen glycosylation between the 3′-methoxy sugar 3 and nucleobase 4, and was carried out by following the protocol developed by Ding, Xiao, and coworkers. 10 The next step involved ammonolysis and sugar deprotection using methanolic ammonia at 100 °C, providing nucleoside 5 in 66% overall yield.…”

Total synthesis of 2'-O-methyl-β-L-arabinosyluridine and reassignment the nucleoside from Penicillium sp. as 2'-O-methyl-β-L-uridine

“…Because only small amount of nucleoside 1 was isolated, its biological activity was not reported by the authors. As our continuous study on total synthesis of naturally occurring nucleosides, we started to carry out its synthesis and investigate its biological activities [12][13][14][15][16][17]. From the synthetic point view, synthesis of β-L-arabinosyluridine could be carried out in two different approaches shown in Figure 2.…”