A chemical investigation of strain RD003821, belonging to the underexplored actinomycetes genus Krasilnikovia, led to the discovery of three novel polyketides: two 20-membered glycomacrolides, krasilnikolides A (1) and B (2), and an aglycone of 1, detalosylkrasilnikolide A (3). A major challenge in the structure elucidation of 1 was to determine the anomeric configuration of the α-l-6-deoxytalose (6dTal) unit, which was achieved by J-based configuration analysis (JBCA) that incorporated anomeric carbon- and proton-specific two-bond 13C-1H spin-spin coupling constants as diagnostic parameters. The updated criteria for the conformation/configuration assignment facilitated discrimination of three out of four stereochemical variants at the anomeric and the adjacent C2 positions, which expanded the scope of the JBCA method to determination of the anomeric configuration of aldohexopyranoses. Compounds 1 and 2 are the first macrolides decorated by 6dTal. Compounds 1-3 exhibited cytotoxicity against P388 murine leukemia cells with IC50 values of 14, 8.4, and 3.9 μM, respectively. In addition, 1-3 were antibacterial against the Gram-positive bacterium Kocuria rhizophila with MIC values of 25, 50, and 100 μg/mL. 1 was inhibitory against Staphylococcus aureus with an MIC of 50 μg/mL.

structure elucidation, a-L-6-deoxytalose, glycomacrolide, Krasilnikovia

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6	C7	C8	C9	C10	C11	C12	C13	C14	C15	C16	C17	C18	C19	C20	C21	C22	C23	C24	C25	C26	C27	C28	C29	C30
3	aL6dTalp	104.2	72.0	67.7	74.4	69.4	16.8
	Subst	175.6	45.9	89.0	133.7	130.7	126.0	143.9	42.4	49.2	134.9	131.2	36.1	72.5	40.6	75.4	138.1	129.9	35.1	85.4	134.0	125.5	13.4	15.2	12.1	24.5	19.3	13.4	10.8	18.1	11.9


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6	H7	H8	H9	H10	H11	H12	H13	H14	H15	H16	H17	H18	H19	H20	H21	H22	H23	H24	H25	H26	H27	H28	H29	H30
3	aL6dTalp	4.88	3.75	3.70	3.57	3.74	1.11
	Subst	-	2.80	3.90	-	5.89	6.04	5.60	2.23	1.83-2.18	-	5.32	2.43	3.23	1.69-1.79	3.97	-	5.12	2.75	4.66	-	5.51	1.57	1.20	1.77	0.99	1.64	0.90	1.63	0.81	-


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6	C7/H7	C8/H8	C9/H9	C10/H10	C11/H11	C12/H12	C13/H13	C14/H14	C15/H15	C16/H16	C17/H17	C18/H18	C19/H19	C20/H20	C21/H21	C22/H22	C23/H23	C24/H24	C25/H25	C26/H26	C27/H27	C28/H28	C29/H29	C30/H30
3	aL6dTalp	104.2/4.88	72.0/3.75	67.7/3.70	74.4/3.57	69.4/3.74	16.8/1.11
	Subst		45.9/2.80	89.0/3.90		130.7/5.89	126.0/6.04	143.9/5.60	42.4/2.23	49.2/1.83-2.18		131.2/5.32	36.1/2.43	72.5/3.23	40.6/1.69-1.79	75.4/3.97		129.9/5.12	35.1/2.75	85.4/4.66		125.5/5.51	13.4/1.57	15.2/1.20	12.1/1.77	24.5/0.99	19.3/1.64	13.4/0.90	10.8/1.63	18.1/0.81	

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

C/C=C(\C)[C@H]1OC(=O)[C@H](C)[C@@H](O[C@@H]2O[C@@H](C)[C@@H](O)[C@@H](O)[C@H]2O)/C(C)=C/C=C/[C@H](C)C/C(C)=C/[C@@H](C)[C@H](O)C[C@@H](O)/C(C)=C/[C@H]1C

634.851 g/mol (C₃₆H₅₈O₉)

First, total synthesis of the cell surface phospholipomannan anchor [β-Manp-(1→2)-β-Manp]n-(1→2)-β-Manp-(1→2)-α-Manp-1→P-(O→6)-α-Manp-(1→2)-Inositol-1-P-(O→1)-phytoceramide of Candida albicans is reported. The target phospholipomannan (PLM) anchor poses synthetic challenges such as the unusual kinetically controlled (1→2)-β-oligomannan domain, anomeric phosphodiester, and unique phytoceramide lipid tail linked to the glycan through a phosphate group. The synthesis of PLM anchor was accomplished using a convergent block synthetic approach using three main appropriately protected building blocks: (1→2)-β-tetramannan repeats, pseudodisaccharide, and phytoceramide-1-H-phosphonate. The most challenging (1→2)-β-tetramannan domain was synthesized in one pot using the preactivation method. The phytoceramide-1-H-phosphonate was synthesized through an enantioselective A3 three-component coupling reaction. Finally, the phytoceramide-1-H-phosphonate moiety was coupled with pseudodisaccharide followed by deacetylation to produce the acceptor, which on subsequent coupling with tetramannosyl-H-phosphonate provided the fully protected PLM anchor. Final deprotection was successfully achieved by Pearlman's hydrogenation.

Candida albicans, total synthesis, phospholipomannan, phytoceramide lipid

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

CCCCCCCCCCCCCCCC(=O)N[C@@H](COP(=O)(O)O[C@H]1[C@@H](O[C@@H]2O[C@H](COP(=O)(O)O[C@@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]3O[C@@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]3O[C@@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]3O[C@@H]3O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]3O)[C@@H](O)[C@H](O)[C@@H]2O)[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O)[C@@H](O)[C@H](O)CCCCCCCCCCCCCC

1688.733 g/mol (C₇₀H₁₃₁NO₄₀P₂)