Abstract
We completed a new and efficient synthesis of D-chalcose (I) and the first synthesis of its C-3 epimer (I′) in nine steps with overall yields of 23% and 24%, respectively. The key steps in the sequence were the formation of the stereocenter on C3 via Grignard reaction, the introduction of the stereogenic center on C2 by Sharpless asymmetric dihydroxylation, the protection of the C1 and C2 hydroxy groups with tert-butyldimethylsilyl trifluoromethanesulfonate (TBSOTf), and the selective cleavage of the primary OTBS ether using catalytic DL-10-camphorsulfonic acid (CSA) in MeOH.
Highlights
Chalcose (4,6-dideoxy-3-O-methyl-D-xylo-hexose, I [1,2]) is a structural component of many macrolide antibiotics, such as chalcomycin [3], neutramycin [4], and lankamycin [5] (Scheme 1)
Acrolein dimer [12], methyl 2-cis-5-hexadienoate [13], and trans-1-methoxy-3-(trimethylsilyloxy)-1,3-butadiene [14] have been utilized as non-carbohydrate precursors during the synthesis of DL-chalcose, but no attempt was made to resolve the racemate
We describe a new and efficient 9-step synthesis of D-chalcose (I) with a 23% overall yield
Summary
Chalcose (4,6-dideoxy-3-O-methyl-D-xylo-hexose, I [1,2]) is a structural component of many macrolide antibiotics, such as chalcomycin [3], neutramycin [4], and lankamycin [5] (Scheme 1). We describe a new and efficient 9-step synthesis of D-chalcose (I) with a 23% overall yield. We proposed that diol 6 should be protected and the primary OH group could be selectively deprotected and oxidized to yield the corresponding aldehyde.
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