Total Syntheses of (+)-Gabosine P, (+)-Gabosine Q, (+)-Gabosine E, (−)-Gabosine G, (−)-Gabosine I, (−)-Gabosine K, (+)-Streptol, and (−)-Uvamalol A by a Diversity-Oriented Approach Featuring Tunable Deprotection Manipulation

Abstract

A new diversity-oriented approach to C7-cyclitols, which possess a broad spectrum of biological activities, is developed. The key polyoxygenated intermediates with different O-protecting groups were accessed by an intramolecular aldol-cyclization of a diketone derived from δ-d-gluconolactone. The versatile intermediates can be easily transformed into structurally different carbasugars based on control of deprotection manipulation. The utility of the robust approach is illustrated by the first syntheses of (+)-gabosines P and Q, as well as the syntheses of several other gabosines and related analogues viz. (+)-gabosine E, (-)-gabosine G, (-)-gabosine I, (-)-gabosine K, (+)-streptol, and (-)-uvamalol A. In addition, the absolute configuration of (-)-uvamalol A is assigned by its total synthesis.

Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone

“…In particular, the intramolecular aldol condensation is an important approach to the formation of ring systems such as cyclic β-hydroxy carbonyl products or cyclic α,β-unsaturated carbonyl products. Therefore, various types of intramolecular aldol-type reactions have been developed and widely applied to the total synthesis of diverse natural products [9][10][11][12][13][14][15][16][17][18]. The reductive aldol-type reaction is another important variation that has been reported using metal catalysts such as Co [19][20][21], Cu [22][23][24][25], and others [26][27][28][29][30][31][32] with hydrosilanes (R 3 Si-H) or hydrogen as the reductant.…”

Sweritranslactones A–C: Unusual Skeleton Secoiridoid Dimers via [4 + 2] Cycloaddition from Swertiamarin

“…However, novel compounds are not easy to obtain using traditional phytochemical methods. Many approaches have been used to obtain privileged structures, including the diversity-oriented chemical modification of natural extracts. − …”

A Flexible and Divergent Strategy to Flavonoids with a Chiral A-Ring Featuring Intramolecular Michael Addition: Stereoselective Synthesis of (+)-Cryptocaryone, (+)-Cryptogione F, and (+)-Cryptocaryanones A and B, as Well as (+)-Cryptochinones A and C

“…After optimizing conditions to provide useful quantities of 31 , the transformation of this key intermediate to 2 and 5 is easy. The silyl group of 31 was removed smoothly with HF·Py to give (+)-cryptogione F. Further β-elimination of the hydroxyl group in 5 with Burgess reagent furnished (+)-cryptocaryone (see Scheme ). The spectroscopic properties of the synthetic samples were identical to those of the natural products. , …”