Total Synthesis ofN-Malayamycin A and Related Bicyclic Purine and Pyrimidine Nucleosides

Abstract

Methods are described for the total synthesis of bicyclic perhydrofuropyran nucleosides as N-analogues of the naturally occurring malayamycin A. Formation of the N-nucleosides relied on the activation of thioglycosides, proceeding via sulfonium intermediates. Ring closure metathesis was used in two approaches to build the bicyclic dioxa heterocycle. Another approach relied on the use of a sugar precursor and cyclization to the bicyclic thioglycoside.

Unequivocal Experimental Evidence for a Unified Lithium Salt-Free Wittig Reaction Mechanism for All Phosphonium Ylide Types: Reactions with β-Heteroatom-Substituted Aldehydes Are Consistently Selective for cis-Oxaphosphetane-Derived Products

“…This is consistent with earlier reports of non-epimerization of this and other related aliphatic aldehydes in Wittig reactions carried out under similar conditions. 89,90,91,92,93,97 Comparing phospholium ylides 50 and 78, it is noticeable that there is a much greater shift from E to Z selectivity for the semi-stabilized analogue 78 in its respective reactions with 66 and 65. Thus it shows complete E-selectivity in its reaction with 66, 98 but very high Z-selectivity in its reaction with 65 (albeit not quite as high as the MePh 2 P-derived analogue), demonstrating a very dramatic shift in the energy of the cisselective TS as a consequence of the presence of the heteroatom.…”

Transition metals in organic synthesis: Highlights for the year 2005

“…(221)) [1117,1118], hybrids of d-galactose with 1-deoxynojirimycin analogs [1119], the tetracyclic core of tetrapentalones [1120], 1-epi aglycon of cripowellins A and B [445], gambieric acid [1121], aspercyclide C [524], radicicol and pochonin C [1122], trachelanthamidine [1123], heliannuols G and H [652], (−)-Geismann-Waiss lactone [1124], tuberostemonines [688], (−)-kendomycin [1125], pochonin D [1126], (−)-223A [1127], coleophomones B-D [1128], brevetoxin B [130], garsubellin A [45], fostriecin [48], 11-acetoxy-4-deoxyasbestin D [1129], (+)-cyclophellitol [1130], ␤-C-glycosides [50], zoapatanol [247], deoxymannojirimycin and swainsonine [1131], valienamine [1132], A 3 adenosine recetor agonists [1133], vincantril [810], (−)-perhydrohistrionicotoxin [1134], annonaceous acetogenins [1135], deoxycombrestatin A-4 analogs [1136], (+)-lentiginosine and analogs [1137], N-malayamycin A [1138], (−)-salicylhalamides A and B [938], oxytocin analogs [1139], steroid-like compounds [440], (−)-isoprelaurefucin [338], halichondrin B [1140], (−)-microcarpalide and (+)-lethaloxin [1141,1142], anamarine …”

Synthesis and multidrug resistance reversal activity of dihydroptychantol A and its novel derivatives

“…32 As shown in Figure 2, the substitution pattern of the hydroxyl group and bromine atom on the fragment CH 2 (7)-CH 2 (8) was confirmed by analysis of its HMBC. After the hydroxyl group was oxidized to a ketone under Swern conditions, 33 the afforded compound 18 reacted with thiourea and thiosemicarbazide, respectively, to yield the thiazoles 19 and 21.…”