Total Synthesis and Absolute Configuration of Sphingofungin D (N-Acetyl Asperfungin)

Synthesis of Sphingofungin D and Its Three Diastereomers

“…In the case of lithium or Scheme 2. Careful examination of their 300-MHz 1 H-NMR spectra (see Figure 1) revealed the spectrum of the more polar product to be identical with that of (2S,3R,4R,5S)-4 derived from sphingofungin C. [3] Especially the magnitude of the coupling constants J 2,3 , J 3,4 and J 4,5 of the more polar product were in good agreement with the values reported for Scheme 5. ); (d) (nBu) 3 SnH, AIBN (92%); (e) I 2 , Et 2 O (95%); (f) 1) EtO 2 CNϭNCO 2 Et, Ph 3 P, PhCO 2 H; 2) K 2 CO 3 distinction between the diastereomers (see Experimental Section).…”

“…The best result was obtained when the coupling was carried out with chromium(II) chloride and nickel chloride in DMSO [15] [16] to give in 41% yield the desired product 20 as a diastereomeric mixture as shown in Scheme 4. ); (d) (nBu) 3 SnH, AIBN (92%); (e) I 2 , Et 2 O (95%); (f) 1) EtO 2 CNϭNCO 2 Et, Ph 3 P, PhCO 2 H; 2) K 2 CO 3 distinction between the diastereomers (see Experimental Section). Synthesis of the nonpolar building block 15; reagents: (a) 1) 1-heptyne (8), nBuLi, BF 3 ·OEt 2 , THF; 2) (R)-7 (80%); (b) Li, tBuOK, H 2 N[CH 2 ] 3 NH 2 (88%); (c) TBSCl, imidazole, DMF (quant.…”

“…Synthesis of the nonpolar building block 15; reagents: (a) 1) 1-heptyne (8), nBuLi, BF 3 ·OEt 2 , THF; 2) (R)-7 (80%); (b) Li, tBuOK, H 2 N[CH 2 ] 3 NH 2 (88%); (c) TBSCl, imidazole, DMF (quant. [3] (b) AcOH, THF, H 2 O (95%); (c) LiOH, THF, H 2 O (78%) The four diastereomers of 4 were then converted into sphingofungin D (1) and its three diastereomers as shown in Scheme 5.…”

Total synthesis of the salicyldehydroproline-containing antibiotic promysalin

“…As the absolute configuration at C2 and C8 was unknown, this method could have the further advantage of providing access to all stereoisomers, by using the appropriate proline as a catalyst. 16 [α]D 23 = -0.6 (c 1.8, CHCl3). Again, Swern oxidation followed by another α -oxyamination reaction allowed the stereoselective introduction of the hydroxy group at C2 in compound 14.…”

Synthesis of acyclic and heterocyclic natural products utilizing cyclitols as novel chiral building blocks

“…Compound 8 was also employed for the total synthesis of the novel antifungal agent sphingofungin D (N-acetyl asperfungin) (Scheme 4). 15 Acidic hydrolysis of the dimethyl acetal group in 8 afforded the corresponding acyclic aldehydo-sugar, whose Wittig reaction with Ph 3 PNCHCO 2 Et provided E-alkene 16. This was transformed into allyl bromide 18 in three steps.…”