Towards the total synthesis of Calyculin C: preparation of the C13–C25 spirocyclic core

Towards the total synthesis of calyculin C: preparation of the C9–C25 spiroketal-dipropionate unit

“…41 As already reported by us 29 and Kuwahara in his total synthesis of pteridic acids A and B, 42 this reaction only gave a moderate yield of the expected ynone. In this case ynone 2 was obtained in an acceptable 50% yield (Scheme 5).…”

“…29 Lactone 14a was reduced in the presence of an excess of LiAlH 4 . Surprisingly, the TBS group was cleaved during the course of the reaction and triol 15 was obtained (Scheme 4).…”

“…29 For coupling of the two key intermediates 3 and 4, we decided to use the method developed by Fukayama (CuI, PdCl 2 (dppf), P-(2-furyl) 3 in a DMF/Et 3 N (5 : 1) mixture at 50…”

Synthesis and Some Properties of 4'-Phenyl-5'-Norcarbocyclic Adenosine Phosphonic Acid Analogues

“…Removal of the benzoyl protecting group of 11 under methanolic ammonium condition (NH 3 /MeOH) provided the primary alcohol 12, which was oxidized to the aldehyde 13 using Swern oxidation conditions (Oxalyl chloride, DMSO, TEA). 12 The aldehyde 13 was subjected to nucleophilic Grignard conditions with vinylmagnesium bromide to give divinyl 14 which was subjected to ring-closing metathesis (RCM) conditions using 2 nd generation Grubbs catalyst 13 to provide phenyl substituted cyclopentenol 15a (34%) and 15b (35%), which were readily separated by silica gel column chromatography. The NOE experiments with cyclopentenols 15a and 15b confirmed these assignments.…”

Conversion of carbonyl compounds to alkynes: general overview and recent developments

“…33 Applying the same conditions to the substrate 25, which is suitable for the synthesis of the natural product, gives only poor conversion and a low yield of 22% of the corresponding aldehyde is obtained (41% yield based on the recovery of the lactol). 34 …”