Syncephalastrum racemosum ATCC 18192 and Mycobacterium rhodochrous ATCC 19067 partially degrade the n-pentyl side chain of cannabidiol, cannabinol, delta8-tetrahydrocannabinol and delta9-tetrahydrocannabinol. Carboxylic acid and alcohol side chain derivatives are major metabolites.
Background:
Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate
capable of undergoing multiple types of transformations due to three key structural features:
a free alkene, a bridged oxygen atom, and a highly strained ring system. Most notably,
ring-opening reactions of OBD using transition metal catalysts and nucleophiles produce
multiple stereocenters in a single step. The resulting dihydronaphthalene framework
is found in many natural products, which have been shown to be biologically active.
Objective:
This review will provide an overview of transition metal-catalyzed reactions
from the past couple of years including cobalt, copper, iridium, nickel, palladium and rhodium-
catalyzed reactions. In addition, the recent derivatization of OBD to
cyclopropanated oxabenzonorbornadiene and its reactivity will be discussed.
Conclusion:
It can be seen from the review, that the work done on this topic has employed the use of many different
transition metal catalysts, with many different nucleophiles, to perform various transformations on the
OBD molecule. Additionally, depending on the catalyst and ligand used, the stereo and regioselectivity of the
product can be controlled, with proposed mechanisms to support the understanding of such reactions. The use
of palladium has also generated a cyclopropanated OBD, with reactivity similar to that of OBD. An additional
reactive site exists at the distal cyclopropane carbon, giving rise to three types of ring-opened products.
The
novel intramolecular ring opening of oxabenzonorbornadienes
with C1-tethered aryl halides was investigated using palladium
catalysts to form fused tetracyclic frameworks. The reaction was generally
found to synthesize 1,2-dihydronaphthalen-1-ol products with mild
selectivity but was capable of synthesizing dehydrated naphthalene
products in excellent yield and selectivity. Substituent effects on
oxabenzonorbornadiene and on the iodoarene were explored along with
the effects of varying tether length, where an efficient reaction
was observed in nearly all cases. A total of 16 examples are reported
with yields ranging from 0 to 96%.
An improved method of the recently reported novel transition metal‐catalyzed intramolecular ring‐opening reaction of oxabenzonorbornadienes with C1‐tethered aryl halides is described. Using a nickel catalyst, fused tetracycles containing a 1,2‐dihydronaphthalen‐1‐ol framework were generated with good to excellent yields and selectivities in most cases: a result seldom obtained using the previous palladium‐catalyzed conditions. Electron‐withdrawing, electron‐donating, and bulky substituents were generally found to be well tolerated in the reaction while extension of the tether led to decreased yields.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.